I use holster molds/blue guns and leave the mold in the holster until it is dry
if i have to use a real gun then I lube it up with thick oil and wrap it in a piece
of saran wrap then let the leather completely dry
the holster don't seem to hold the gun as snugly when pulling the gun out before the leather is completely dry.
I will also periodically press the leather against the mold while the leather is still damp to ensure that the holster forms to the shape of the mold or gun as snugly as possible I think it makes for a better looking pancake or paddle holster and friction sheathes that way,but that is just me...
YMMV