Martyhh
I usually brush paint my models. I find that when I thin the paint, I wind up with lots of air bubbles in the paint, which then get painted on to the plastic. Also the paint goes on very streaky. Suggestions?
I think you're thinning your paint too much. I'll get bubbles in my paint when I have thinned them too much. I find, though, that I can pass the brush over the area again and release the bubbles while the paint levels.
I don't use any additives, but you could also try adding a leveling medium to your paint.
What kind of paint are you using, too? Water-based acrylics? Other types of acrylics? Enamels? Lacquers?* That can have a bearing on how much they should be thinned.
99.99% of my hand-brushing is on figures, and mostly with water-based acrylics, like Andrea, Vallejo Model Color, and craft store brands like Americana, Folk Art, and Apple Barrel. I use a wet palette and it provides just the right consistency for my use.
I have painted models by hand, just to see. I found that I could lay down coats as thin as if I had airbrushed them. Two coats, applied at right angles to help hide any brush strokes.
I also use Tamiya acrylics, thinned with their proprietary thinner. With those, I use a ceramic palette, or even just the jar lid. I'll pick up color on the brush, dip it lightly in a jar of the thinner, then apply it to the piece. Again, it's just the right consistency for my use.
But it all comes back to consistency. When I see air bubbles in the paint on the piece, I know my paint is too thin. That's what I would check-try thinning the paint to a slightly thicker consistency than you're using.
Hope that helps!
Best regards,
Brad
*Yes, guys, lacquers can be hand-brushed, it's a technique. It's popular with Japanese modelers.