The proper method for you to polish a mould would be to use very fine valve grinding paste on a bullet that has been cast in the cavity to be polished. Drill a hole centered in the bullet base, insert a screw, cut off the head, turn the screw in a drill press at slow speed, with the mould closed and locked up. However, the very best cure is probably a new mould. 99.9% of the time any rust has pitted the surface.
A good releasing agent for a mould is the spray made by Frankfort Arsenal called Drop Out. Smoke in a mould is at best a joke, more like an old wives tail.
If you want to try polishing her up, OK. Then, get some Drop Out, heat the mould up by placing it on top of the moulten lead. Let it sit until it is hot, ready to cast, spray her and try a few bullets.
I have won several cast bullet state, regional, national and international chanpionships using the following alloy:
The alloy can be achieved, aproxamately, by using 6 parts of cleaned and fluxed wheel weights, 3 parts of cleaned lynotype and 1 part of chilled lead shot. The chilled shot adds the arsnic, regular soft shot can not be used.
The alloy, water drops to 22 Brinnell and heat treats to 34. With LBT Blue lube and a gascheck the 34 will shoot to 2,800 fps without leading.
Veral Smith may still be around, bless his crotchety old heart. His casting products are second to none. LBT is or was his baby.
By the by, I use a 100 pound production pot to make the alloy once a year, then cast the alloy in muffin tins. I do several pot fulls at a time. I then use up to two RCBS Pro Melt pots and 4 moulds each to cast my bullets. The four moulds allow me to regulate the mould tempratures. I drop the bullets into clean water. I use LBT Blue lube for all of my bullets and use only Hornady gaschecks.