so it sounds like your talking about using as the casting medium for the mask slush latex? if so you probably could get by with just brushing on the ultracal or what ever gypsum medium your going to be using. me personaly i would set the head down and make a damn wall around it so as you know your are getting a nice thick mold. if you are going supper cheap then sure you can just brush it on then put on the rest but you will have to wait for the gypsum to start to go so as it will not just pour off the side. even if you do wait for it to go or start to heat up you will still need to work it and keep pulling it bak up. it is more work and time to make the damn wall but at least if you have the clay to do it go for it you will be much happier with the end product. just my thoughts hope they help. a great resource fro how to is alfreys mold making dvd. best of luck to you. show us a pic of the sculpt. you may want to make two pulls also as the second pull of a new mold is usualy better then the first as no matter how much you try dust or this and that get left behind but hey in our business the fuglier the better right!?