Wash down a plastic model

That's a good thing to do.  I usually wash mine in dish soap before priming or painting- gets the oil from my  grubby fingers off of it.  I let it air dry a couple days before painting.

I never have washed any of my models over the years and it has worked well for me.

I have washed my resin accessories and fruil tracks,but thats all that I have found necessary.

I also have never washed the plastic but do wash the resin am stuff. If I get greasy prints during the building stage then I wipe the area with a small cotton pad and rubbing alcohol.

I have not washed plastic parts either, and there was me thinking I was the only one. I have recently started washing resin parts as have had a couple of issues when painting.

I wash mine with gentle dish detergent or non perfumed laundry soap (Purex Clear). Rinse and pat dry. I can't wait 2 days for parts to dry before doing a kit. LOL!

I know a lot of people do this. I find it unnecessary. During the build it's going to get filthy and accumulate oils from the skin and god knows what. It's all fine and good, but you really SHOULD be cleaning the model before painting again anyway, so I skip this step.

Before painting I dampen a cloth with alcohol and give the model a good cleaning. Since doing this I've had zero paint lift issues.

I have always washed the model, before assembly and again before the painting. (for pre-paint, I use Plastic Prep, until my last bottle runs out)

I used to use warm water for the wash, and warm water for the rinse.  But, just about a year ago, I changed that to warm soapy water for the washing, and cold water for the rinsing. I did that based on a blog post I read about how soap is best absorbed in water. A warm rinse mixes with the soapy water you are trying to rinse off, and a cold rinse chases the soapy water off without mixing in with it, which is the whole reason for rinsing in the first place.

Rex

I used to wash the model before assembly, but I found it unnecessary because the model would become dirty during building sessions.  Nowadays, I wipe the model with IPA before priming it (I use a big make-up brush),

I wash a kit before starting a build "when I think of it"!!! Usually I'm into the build before I realize I didn't wash it.

I do wash a build if I've done some sanding, filing, or handling. This is especially true if the final build is going to be something with a gloss finish. Like a showroom automobile or shinny metallic spaceship.

The way I look at it is washing may not help but it certainly won't do any harm, assuming you use common sense and not try to paint a wet model or allow water to pool in cavities.