1) Model air ( Vallejo) have what they refer to as "varnish" in gloss, satin, and matt - Should I use the gloss varnish , apply decals, then use matt to get my flat back ( airplanes for now )? ........yes
2) Could I use instead, something like Future for the gloss, decal, then use matt varnish? ........yes
3) I have the micro sol and micro set bottles, and I am a bit confused if I need both, and if they are compatible with either of the gloss coats I ask about above? ........One is used to give your decals a gentle helper in adhering to the surface (-set, I think), the other is more aggressive with the decal, for use on compound curves, or where you are running over a non-uniform surface. May be safer to use the -set first just to check the compatibility with your decals, but I usually go right for the -sol.
4) Finally, there is what I think the equivalent to micro sol and micro set in model air line called decal medium and decal fix - should I use these instead? ........Can't say that I've ever used any of their products, but it's generally safest to use products from the same manufacturer. That being said, I've never had problems with Micro-set or -sol over Future.
Thanks for your help - still learning and working on my first project - a Revel Me-410 ........Nice kit with a little work, I built one ages ago & have another in the stash. post pics when you can!