Air test 6'' Foden

I am about to do an air test using a compression 50L using standard female 12mm screw end on the air line. standard for a spray gun attachement.
I want to connect to the water check valve part ref : F62835 which is a male thread model engineering 9/16' x 26 tpi. set on the smoke box side.

Has any body done it this way and what was the adaptor they ended up using?
Make their own or adaption of air hose adaptor?
thanks

I normally use the blowdown valve and just put a hose and clip over the tail pipe