Hi, I've always had real good luck with Model Masters Lacquer Overcoat, in either the Gloss, Semi-gloss, or Flat fihishes. I'e put it over Tamiya, Model Master, and Polly S paints with no problem. I use the Gloss on the vehicles before putting on decals as I've heard it's suppose to give a real smooth finish so the decals can settle down real nicely; plus a little decal setting solution as well. Then, when they are dry I, re-spray with either the semi gloss or the flat to seal everything.
I've also heard that a good clear finish is supposed to hep protect the paint and decals from the harsher oil washes and other scrubbing type or actions in the weathering process.
And I've also heard, but haven't tried it yet, that this clear 'covering' is supposed to work to seal on any pastel chalks too.
Haven't tried the Future yet, but I've heard good things about that too.
Take care, sgirty