If you cannot swap it out with someone for 3F, I'd suggest use it until you can get 3F.
As to dirty, I doubt that, personally. I've used 2F in .40 and .36 without noticing any more
dirty shooting, but then, with the loads we use, there is no buildup of fouling, except on the
outside of the barrel around the lock.
I would think about 40gr. of 2F should give the equivalence of 35gr. 3F, which just happened to
be the accuracy load in my .32 (48" twist).