I also just had a thought about asking for paint thinning advice online.
People should go ahead and ask if they don't know. But, then, the very best money saving tip that anyone can give is to test out that advice for yourself. Go to a Michael's (or Moore's, etc) and get one of those round paint palettes (less than $2 US).
Then mix up that "great woop-dee-do" idea with a few drops of your paint and the thinner, retarder, thickener, etc in one of the dimples. Look at it now and then, poke it with a toothpick,,,,see if it separates, or never hardens, etc.
If you see it separate or turn to goop, or never dry,,,,or anything that you don't like about it, then you might have just saved an $8 brush or your airbrush.
AFTER you know that the stuff mixes together,,,,,,,,THEN you can put it through your airbrush and practice with thinning ratios, and spraying on spare model parts or plastic sheets.
that dish soap tip being mixed up is the exact example of why we shouldn't just "jump right in" and use some online tip without testing first, no matter who has what "online rep",,,,,,,,that guy won't be the one buying a brand new Thayer Chandler XYZ-1234 for you if you mess it up.
Rex