There is a tutorial on delegating SP in this post here: https://steemit.com/delegation/@timcliff/tutorial-how-to-delegate-sp-to-another-user-using-the-steemconnect-tool-from-busy-org I've used it before and it works perfectly. In order to "un-delegate" you (should) simply need to set the delegation amount to 0. I've undelegated before and this has worked for me. Good luck! (but really it should work no problem)