Well Ben I hope I didn't open a can of worms with my statement, I prefer the MIG thinners mainly because there is little else available here in Dublin. The stuff from the DIY shops I find a little hard and smelly but I think the real answer when it gets to washes that work best is use the best you can afford, its all practice and technique.
I would love to try the rain marks stuff, looks great. I think it could be done with Tamiya acrylics just as good but I would practice on a scrap model first.
There are others from art supply shops but this is down to preference. To put it another way, I refuse to use Rowney oil paint because I find it gets "Bitty" kinda breaks into pigment when diluted too much but I love Windsor & newton works a treat and believe it or not I have tubes that must be at least 15 Years old and still useable.
The MIG oils are beautiful. They kinda remind me of the Rembrandt range that was in vogue years ago but have become hard to find. I only know of one supplier in Folkstone.
My main sources of paint for the last 10 years have to be VAllejo and games workshop, excellent stuff. The games workshop "Foundation Colours" are excellent. they can be applied very dilute.
I use Windsor and newton oils.
Last year Robin from Cammet put me onto life colour, again excellent. I love their oilstains etc..
As for protection of the paint. I Always prime. My preference is REvell Basecoat, but if I can't get that I use Gamesworkshop stuff from the aersol.
Before Decalling I paint the areas with Johnsons Klear just for the gloss finish. Then on with the decals and my favourite tool in the whole world Micro sol, I could easily name micro sol as a hobby. I used to do a lot of formula one cars and loved applying the Decals.
Before I start washes etc. YES I do hit the surface with Humbrol matt49 from theh airbrush with about a 50/50 mix and give it about 3to 4 days drying time. Sometimes I use Vallejo matt from their AIR range. I always put a barrier but I change according to how lazy I'm feeling. I find Humbrol matt 49 the best but cleaning the airbrush is not one of my favourite pastimes.