Fujimi 109K finished pastel mottle and dubious markings

[NARSES2]

Other paints are more problematic (LifeColor paints, for example, don't seem to react well to being thinned at all).

I use Lifecolor quite a lot (brush painting) and yes thinning can be fun but thankfully for brush use it's normally ok out of the jar. When it thickens up a bit, which the original "clear" plastic jars were prone to do I found tap water fine.

[Dork the kit slayer]

Allan if you use acrylics, a piece of denim or kitchen roll will polish smooth the paint work before the clear coat.