I've never seen paint melt the vinyl but some paints simply won't dry on it. I've painted the lettering on model car tires and had it still sticky after six months or more. I'm afraid this may be what happened to you. If you can paint over it though great! Only other thing I know to do is to strip it and start over. 

Sometimes it's hard to tell what will work and what won't. I like to apply a test coat to a scrap piece I cut off before using the paint on the actual model.

oh yeah about the paint.... I think acrylic is the way to go for sure... I primed it with some regular cheap flat black spray paint like I normally use... I did a ton of miniatures for games like Warhammer, Warhammer 40k, Necromunda, etc, etc and always used a black spray primer and got good results no matter if I used an expensive spray or cheap k-mart spray (ok that may be showing my age there lol) but with this PVC it feels funky... I'm not sure how to explain it but it feels.....ummmm..... maybe sticky is the word... almost like its bleeding out the model... its the weirdest thing because it feels oily at the same time but when you set it down and look at your fingers there's nothing on them but touching the model you expect something to be there... like I said its a weird condition... but looking at the model it looks fine it just feels weird and it didn't feel like this until I primed it.... maybe I should have looked for acrylic spray paint or something along those lines but with this lockdown and stored being closed I just went with what I had... other than being a larger scale than what I'm used to painting (human skin wise) it's going ok and once I get a coat onto the primer it seems fine... guess its just more learning with a new material, I'll know better next time

thanks, guys... yeah some of these tips I've learned along the way... there was extreme flashing on the parts like 1/2 inch to inch extra on most parts, like arms and her boots and it was nerve-wracking, to cut off to say the least...  I was so afraid of cutting into the parts because it's soft yet firm at the same time, I know that sounds weird but it was a weird experience... I like the blow dryer idea that would have helped a ton had I thought of it... the water just sounded too easy to mess up and not be able to control but the hairdryer is brilliant I could control it a little more I think....  I doubt I go looking for a pvc kit but who knows what will come along.... thanks a ton

Well, I generally fill the legs with plaster to get a more balanced bottom-heavy figure. I can see doing the same to your base. 

I've never filled the top with anything. So far I've had no problems - cross your fingers... 

As R said, vinyl is more accurate.

i second expanding foam, the kind used to seal around pipe penetrations through walls.

i use it in vacuum formed models to stiffen them. It expands ALOT.

You want to avoid anything that gives off heat when it cures.

Try to stick the part in ice water as deep as feasible.

Aha!

 Rare kits indeed.The methods are wide ranging. I have set any I have done in a thin layer of Hydrocal because they needed weight when built!

I've built one and plasters not the way to go if you need to fill a lot of space, you want expanding foam instead. The vinyl will wilt over time and you need something inside it to support it's shape, which plaster can be too heavy for. Plaster also heats up when it dries and that can severely warp a kit like this if you're not careful.

The materials easy enough to work with. When cutting off the excess warm the material in some water so it softens a touch and is easier to cut into.

Not much more to say about it TBH. They're usually really easy kits to put together. It's mostly about building internal support structures and not applying too much expanding foam (it will warp if you do)

I've never built a PVC kit, either, but a buddy of mine does.  He likes comic book/superhero subjects, and a lot of kits of those subjects come from Japan, and are in vinyl.  He does fill the parts with plaster, or sometimes with crumpled newsprint or tinfoil.  Filling the parts helps them retain their shape, especially since it's necessary sometimes to apply heat with a hair dryer during assembly, and to keep their shape once the figure is done.

There are PVC kits of other subjects, too, like dinosaurs or other prehistoric animals.  Same thing-you fill the cavities with plaster, to hold the shape.

   I have never worked on a pvc kit, hydrocal is light weight so you may need something more substantial to support your model, never hurts to have a heavy base for any kit.

    IF you have reached assembly, my smart phone is smarter than me....couldn't see your pictures. Anyway a good sharp #11 blade should clear any flash off your parts, not sure if pvc is sandable?? If I recall normal model glue will not bond pvc, you will need epoxy or simple CA (super glue).

     I heard from a friend who did an old ED-209 from Robocop, and he says that enamel or laquer paints are NOT recommended. Apparently they melt the vinyl. Acrylic s are the way to go.

ok guys here is the pictures of the model I'm working on and the base.... its pvc and theres a woman that stands on this base and someone told me I needed to fill the base... I guess to give it strength or something.... they said plaster or something like that... does that sound right??? and if so hydrocal or reg plaster or something else

https://www.facebook.com/photo.php?fbid=10158591840732052&set=pcb.10158591842872052&type=3&theater

https://www.facebook.com/photo.php?fbid=10158580977297052&set=pcb.10158581039677052&type=3&theater

https://www.facebook.com/photo.php?fbid=10158574626042052&set=pcb.10158574636377052&type=3&theater

https://www.facebook.com/photo.php?fbid=10158574404927052&set=pcb.10158574483212052&type=3&theater