Oil wash over Future = confusion..

Only if there was a break or 'hole' in the top coat of Future would the enamel thinner attack the underlying paint. I suspect you sprayed the Future in a few light coats, I brush it on heavy avoiding bubbles and have had no issues.

If the underlying paint is acrylic then there is no need for the protective gloss layer of Future.

* Future requires 24 hours + to fully cure depending on temperature & humidity.

Enamel thinner is aggressive so do the oil wash fast & light.

Fully cured (2-3 days), it should not attack the Future at all. As SF pointed out, if you are using acrylic paint, then there's no need for the gloss unless you are applying decals, or you have certain sharp details that you want to isolate and don't want the wash to darken the whole area. Make sure the Future coat is thick enough to seal the topcoat. When using Future to gloss the area for decals, make sure to wait a couple of days to let it cure, otherwise the water and the decal setting solution will cloud and haze the Future around the decal.

Try picking up some Mona Lisa Odorless Thinner from Hobby Lobby. It's very gentle. I've used it to do oil washes over enamel with zero problems.

Yes, I did spray the future in a couple of light coats to avoid it start running, but it cured for several days before I tried the wash. I have seen it being suggested many times to put a coat of future down before the wash since it will help wiping the excess off and keep the wash from penetrating the coat of paint. Is there even a big difference between using an oil/thinner wash vs an acrylic/water wash?
Right now I'm just testing stuff on empty plastic bottles before I try it on my first "new" build, but there's so much to take in getting back into the hobby. A lot of new stuff since the last time I've build a model..

Thanks for the info DogsATX, I'll give that a try.

You have to be aware of the thinners chemical make up. If the thinner has a high alcohol or ammonia content it will attack the Future.

I use odorless mineral spirits for oil-based washes over Future all the time and it's never attacked it, but as stated and as you already know the Future needs to be evenly coated and fully cured (not just dry), and also heed Gerald's advice about knowing the chemical content of the brand of mineral spirits. I use Gemini brand that I get from the local arts & crafts store, no problems yet. Turpenoid is also O.K.

BTW, you generally don't want to use a wash based on the same medium as the top coat of paint, and that includes an acrylic-based wash over a Future overcoat since Future is acrylic-based.

People variously use acrylic vs. oil-based or enamel washes and ultimately it boils down to personal preference and the general rule about avoiding using the same medium for the wash as the top coat of paint. Personally I prefer an oil/mineral spirits wash since it won't react with any paint whether it's lacquer, enamel, or acrylic and I've always gotten good results with it.

I generally use testor's enamel thinner + artist oils over future and I like the results.

But the other day I experimented with some turpetine substitute.  And the damn thing not only lifted the future and the acrylic in 2 seconds, it ate into the plastic and started to attack the surface!

I recommend -

1) Tamiya Acrylic.  2) Future to seal, 3) wash with artist oils mixed with testor's enamel thinner.

Thanks for all the great feedback, guys!
I didn't realize just how much of a difference it will make getting the "right" kind of thinner. Between the Acetone, the Isopropyl, the lacquer thinner, demineralized water, thinned Windex and "bad" mineral spirits - it's starting to look like a chemistry lab here..