In the current issue of "The Fouling Shot" (#174), there is a brief article by Jay Dye (a machinist/gunsmith I think), desribing two products that may be of interest:
NAPA dgf 123 (dry graphite film) that sounds perfect for sprue plates & mold tops, maybe even mold cavities. The author gives it a 4- star (out of 5) rating. It retails for $5.75/can.
B'LASTER PB is a penetrating oil which doubles as a bbl./Pb solvent and rust remover that Dye rates as 5-star (out of 5). True Value hardware stores have it for $4 - $6 per can.
I've already ordered the NAPA dgf 123 and will look into B'LASTER PB soon. ...Maven