If it's an actual Buck Boiler brand, they're really specific about what you can put in the water becuase apparently it can trip the breaker on the element and then you need to start over.
You need to use powdered dishwashing detergent (I think they recommend Cascade) and I think you can put a max of 3 teaspoons in it. They have really good directions that come with them, so just read through them & follow them & you'll be fine. I don't think you want to use liquid soap in them or it will mess up the element.
You definitely need to check on the water ever hour or 2 (not sure it says to do it that often, but from experience, you'll want to) and keep it full otherwise it will evaporate off and the whole skull won't be submerged- use HOT water when you refill it so it doesn't take as long to get to boiling again.
I've left a couple skulls in too long and they got really brittle (which will happen with any boiling method). I started to keep it in there until the little bit of meat that's left on the skull starts to turn color & look 'cooked' and then hose it off. If it won't all come off, I put it in for another hour or 90 minutes and try again.
If you can keep the antlers out of the water, try to, otherwise you can get the clean if you either scrub them really good with hot water or powerwash them, but you want to do that right away (like within 30 minutes or so) from taking it out. Otherwise all that nasty crap will be on them & it's a pain to get off. Looks like someone else has another method to keep the antlers clean that might work too.
Good luck!