Don't worry about getting all the solder off.
Heat the wire side while the rx8 is held down (rubber vice, servo tape to workbench, etc). While heating each wire at the joint, use a pair of needle nose pliers (or anything that won't melt really) to gently pull the wire away from the rx8. As soon as the solder liquifies, that gentle pressure will pull the wire off of the posts, along with the heat source, and everything will be perfectly reusable...basically with both sides tinned.
Repeat for each wire.