Rustin's clear plastic floor coating, "satin finish" works very well. Bit fiddly to mix as its not exactly a two pack resin, it only uses a tiny amount of hardener. I used the syringes you get with printer cartridge ink refills, much easier than trying to measure into a container. Easy to brush or spray and fairly cheap, unfortunately the smallest pack size is 1 litre. Gives a good finish, doesn't seem to dissolve cured paint or lift decals, and cures ready to use in two hours.