A mould going into storage gets oiled with Ed's Red or plain Automatic Transmission Fluid. I immerse the oiled mould in mineral spirits or paint thinner, slosh it around well and plow it dry with compressed air when ready to use again. Heat the mould on edge of melting pot while lead melts and good bullets from the start.
For me, the mineral spirit works better as a degreaser than acetone. All acetone is probably equal. Beware the use of brake cleaner as it can release some EVIL gas when heated.