rent the setup you need from Home Depot.

I have a Porter Cable BN200 (18 gage 2"max) Brad nailer and a Accuset (16 gage
2 1/2"max) Brad nailer.

Both get only occasional use; PC was a gift & I bought the Accuset used for
$60.

Base molding; shot into sill & studs (use stud finder if you must) you'll be
able to tell the "misses"

Crown; shoot into studs & joists

18 gage makes much small "holes" in molding. 16 gage holds better but the
holes are bigger. 15 gage probably more than needed.

prime & prepaint molding; install fill with no-shrink spackle, touch up; done

YMMV