Dear Footski,
It's impossible that I am the only one to come up with treating flags in this way, others I am sure must have done this before me (and still doing it), so I am only 're-inventing the wheel' so to speak!
The basic principal of use is also very easy. Leave the flag on the support paper it comes on (BECC presentation), carefully pull back the flag together with the sticky bit so it stands upright without flopping back. Once this is done all is ready for spraying. Lightly wet both sides with the spray varnish. During the drying stage, turn upside down so the flag hangs down so that it touches nothing.
Please bear in mind that I am using Humbrol spray tins (Matt varnish), so, if anyone is mixing for application via their own spray guns (rather than buying the prepared spray tins), I should imagine that the dilution will be much the same as if one was diluting paint for spraying. The drying time stated on the prepared spray tins says 15mins, and this is true, as I have treated my Belfast with same (in direct sun), and it does go off very quickly. However, after treating the flags, and giving them about 1/2 an hour initial drying time, I put them in the airing cupboard over night, and they are 100% and ready for use. If sprayed outside in direct hot sun, and 'hung' as prev. mentioned, the flags can be ready within the hour.
Please spread this info. about, as it saves lot's of time and gives excellent results.
Regards, Bernard