It is pretty popular in US porn and sound a lil' perverted, but there are not a lot of asslicking Eurobabes pictures so I start with JENNIFER DARK (posted also on IR Eurobabes).
I had a Spanish-Brazilian girl that was great on this, to date the only personal experience I have on this exercise
http://www.porn2free.com/galleries/mc/bca/16/interracialtip.html