Acetone is one of the most versatile and useful things to have around when you have a printer that uses ABS such as the Replicator 2X. It serves as a great way to clean off your build plate as well as to promote adhesion between your part and the kapton tape. Acetone also happens to have a few more uses with ABS.
First off you can use it to glue multi-part prints together. This is incredibly useful when you want to either make smaller more manageable prints out of a bigger print, or if you want to print something bigger than your build volume. To use acetone as glue for ABS you simply brush it on each side of a joint and press the parts together and it will become somewhat stuck fairly quickly and fully dry in about a day.
Acetone can also be used as a method to touch-up and smooth any problem areas that didn’t quite turn out right but aren’t worth reprinting the part over. You simply paint it on with a brush and with light pressure it will blend the outer layers of the print for a much smoother look.
If you are planning to try using acetone it is recommended to first attempt it on a scrap piece as it can very quickly ruin a print if you significantly over apply it. For additional information on using acetone to finish prints check out this very informative post on 3Dprint.com.