From here you can find different cleaners for cleaning the ski base from dirt and old wax.

Wax remover , base cleaner - for removing a grip was (not recommended for glide zones)

Glide cleaner, Racing cleaner-  for cleaning the glide zone from dirt and old wax/fluor

Fluoro cleaner- Same as Glide cleaner, but it contains fluoro!

For best result use a good quality fiber paper.