Inspect & clean the mould carefully ,inspect with magnification for burrs or misplaced parts that may hold the blocks open, mainly the guide pins on 6 bangers.
To get the cavitys cleaned up cast a few bullets & keep em relative to the cavity from which they came. Next drill an appropriate sized hole for a tap , put the tap in a drill, cover bullet with a comet cleanser/h20 paste & spin em slowly in the cavitys.
It won`t take much so go slow, too much will round sharp corners
The mould will not need smokin after the Leementing process.
& go to castboolit site & search Bullshops sprue plate lube , anybody with an aluminum mould has got to have some on hand!!
His link on the site says he`s closed , but I hear he`s at least shippin lubes .