As far as oils and weathering go, I use artist's oils (Schminke-Mussini) and mineral spirits, and never have any problems with it attacking plastic.
I generally don't use Mig or AK products. Nor Tamiya's weathering, washes, etc, or similar products from other brands. I appreciate that they take the guesswork out of making things like washes, or weathering powders, and so on. And that's a definitely attractive quality, especially for people entering the hobby. But I know how to make those kinds of things myself, from components I have on hand. To each, his own, of course.