I've been retrofitting an existing PVC irrigation system around my house. Part of that work requires that I work in shallow holes adding T joints and elbows in places where there were none before. In an effort to measure twice and cut once, I've been assembling the system without glue to make sure I have the layout correct. More often than not however I'm running into issues separating the slip joints and pipes despite the fact they aren't yet glued.
What's the best way to separate these joints? Should I be applying some sort of lubricant beforehand (that won't affect gluing later on) or is there a trick beyond forcing things? With too much force I'm afraid I'm going to break pre-existing joints or mangle the existing fittings.