The easiest way I’ve found to get the last bit of wax out of a glass jar is to put the whole thing into the freezer overnight. The next day you can easily pry the harden wax out of the jar with a blunt knife.
If you have any residue wax left over try rubbing it with a paper towel and a bit of baby oil until clean then wash in warm soapy water and rinse and dry.
Peel off any labels. If the bottom label doesn’t comply, place the jar in a little bit of warm soapy water for a few minutes and it should then peel off easily.