I use manteca de corojo to keep the skin on my hands from drying out and cracking, especially in the winter time. I haven't found over years that it does much to help the sound of the drum skin, and too much may make some skins sound duller. What I do use it for is to replace the natural oils of the drum skin after I clean it. I clean the drum skins with rubbing alcohol (rum works pretty well too), especially if there is blood on it. The alcohol takes some of the natural oils out of the skin, and I use manteca de corojo to replace the oils and keep the skin from getting too dried out.
The big problem with manteca de corojo is it will permanently discolor white clothes if you let it get on them. Some people prefer shea butter, olive oil, or other vegetable fats for that reason. I have even seen one of the top drummers in NYC use butter on his hands when he had nothing else in a winter time restaurant gig.
You can get it online. One of the biggest online botanicas is at:
http://www.folkcuba.com/stores/hm_lucum ... ubCatID=30You can get a half pound for 2 bucks plus postage, or a 55 gallon drum for $520, your choice. It does go rancid in the heat, so I the smallest quantity will be fine.