Wash .....wash-out

I now there are about a zillion questions on washes, and i have read probably half of those, but for such an important procedure, I m stil having some issues.

I am mixing up the 'tinted-thinner' as described im most articles, but I wonder if Im making it too thin because while the panel lines turn dark when I first apply the wash, the color tends to evaporate in a few minutes.

Do I need to apply more 'coats' or more pain in my mix.

Also......how do I keep from wiping away my base paint when i wipe away the wash spillover later on?

Will Future prevent the loss of my base paint?

I appreciate any comments.