I follow a fairly strict regimen when bumping up the .452 slugs. I use both home cast WW alloy & commercial hard cast ( purchased from a commercial caster unlubed & unsized by him @ $0.06 each) interchangeable. With the coating bullet alloy doesn't seen to be an issue like it is with wax lubed slugs. Different powders will require more or less coatings ( at least 2 and sometimes 3 coatings) to get up to .460 or more, once they are all above .460 ( I will measure a handful out of a couple hundred bullets) I push every one through a .459 sizing die. The sizing die is left dry so no oils contaminates the coating. Some that take a hard push if the coating is a bit thick and some go through very easy but as long as the sides touch the die body I use them.
I should add that "shake& bake" puts a thicker coating per layer that the Electro-static gun seems to apply.
I wont deny it is a bit of a chore more than just using conventional lubed slugs but the lack of concern over alloy content from cast session to session with scavenged lead and the accuracy i can achieve wuthout heavy recoil and with very cheap to produce ammo make it viable for me.