Not sure if this is the right place for this thread, but:
http://nocturna-fangor.tumblr.com/post/66085991848/solution-to-the-monster-high-greasy-hair-glue-seepage
I just found this method for fixing (or rather, "fixing") the hair glue seepage problem in dolls like MH and Barbie. Basically it involves lots and lots of talcum powder. Apparently it's not a new trick, but I've never heard of it before so I thought I might as well put it here. I have no idea if it works (or how long effect will last, or what happens if you get the head wet etc) but it seems OP had some favorable results. I'm trying it on a thrifted doll at the moment, will let you know how it works out (current status: powder everywhere, and also I need a better brush).