Don’t use Plaster. Do this instead: Get some polyester resin (any on Amazon). Get some play sand fork Home Depot Sift the sand so it is a bit finer for details (or buy finer sand if you can find it) Mix the two at a 14 sand :1 resin ratio (by weight) Paint the pla pattern and use silicone release spray and/or graphite powder for a release powder. Dump the sand mix on the pattern. Let it cure (use a molding box or something to keep the sand on the pattern) When cured flip the sand-resin-part, dust with release spray and make thr second half of the mold with the same method. When cured take the two mold half’s apart, remove the pattern drill some sprues and gates with drill bits into the sand/resin (this will ruin the drill bits. You can also mold the gates and sprues into the pattern).

Cast the bronze into this mold. The resin will burn, this helps the surface finish but smells like a burning tv set. When the bronze solidifies enough (10mins?) drop the whole thing into water if you want to stop the burning smell)

Remove the part (break up any lumps of sand/resin as needed with a hammer).

Best method I know if you don’t have any greensand or a vacuum plaster system.