Why not let the gun just sit in the holster for a couple days, then do a handful of "test" drawing/reholstering? Might well be all that it needs.
If you absolutely, positively can't get any improvement without a bit of help, the thin baggie approach is a method that some find useful. The risk is, it can loosen up a gun just enough to the point of being too much, if you're not careful. A little bit goes a long way, here. (And, with most holsters, there's no real going back, as there's no tensioning screw if you screw it up.)