I've been using the Testors MM A/B thinner for years and getting great results. I recently started using just mineral spirits from Home Depot to mix, and had a problem with dry-spray.
I was painting my 1/48th Osprey with MM Dark Ghost Gray thinned with generic HD mineral spirits, and got the pebbly finish. I know many things could cause that but I just thought it might be because I used regular mineral spirits to thin the paint, which may dry (in flight so to speak) faster than the Testors.
I always thought the Testors thinner was much more refined and possibly has a slight retarder in it. So no more thinning with normal min spirits for me. Using it to clean is one thing but to mix I will spend the extra.
Any thoughts on the Testors formula compared to hardware store min spirits?