Future and Windex Questions

I'm not sure what you mean by "leaves a visible seam when dried."

Future has very good self leveling properties, but as Matt Swann says, if it pools in spots, it's best to soak it up while still liquid using a paper towel.

Windex will dissolve any acrylic coating on which I have tried it.  So will any other solvent that works on acrylic, just as using mineral spirits, paint thinner, etc. will dissolve enamels.

If you are satisfied with a paint job, but are worried that you may have to strip part or all of the overlying coat, give the model a light coating of artist's workable fixative, available at artist's supply stores. This will seal the underlying paint and provide some protection if you have to strip the top coat.

You probably wiped off the thin coat of future...and unknowingly got down to the paint layer.

Once you have a few light coats of future on, you can go with the last "wet" coat. Avoiding pooling is basically a test of your airbrush control. Low pressure and keep the AB moving. The only thing that really helped me was practice. I dug out and old, busted up model, and practiced on that before I "commited" my first future build. It did take a few attempts, but it helped a lot and gave me a sense of what it would take to get it just right.

That model is still my "practice" model. It's saved me many headaches, but it does take a little discipline and extra time to trial run new techniques.