Not trying to make fun, 'wax specialist' isn't a term I am familiar with but then again what else could you be referring to...somehow I doubt cars or floors...
Contact Happy Sun Yoga at info@happysunyoga and ask for the contact info of the woman offering depilacion and mani/pedis. I believe she's British and a real hoot. The studio is in Barrio Norte, on French close to Laprida.
full disclosure: I'm a teacher at the studio, but I don't do waxing, sorry!
There's another place I had pretty good experience with, if one can ever consider waxing a good experience, I can't remember the name but it's a small place on one of the blocks bounding a small plaza near Parque Las Heras, Scalbrini Ortiz/Cabello/Salguero/Las Heras, you'll see a Starbucks on one of those corners. You can't miss it, big white sign with black letters shouting 'DEPILACION'. It wasn't expensive and the place was clean and well managed and quite busy.
Not a lot of English spoken, but what could be a funnier language learning experience then to find out exactly what cavado, cavado profundo, tira de cola and tira de ano mean?