When beading with Soft Flex, or any other beading wire, I never cut the full length of wire I need. First, I pull out a small amount of soft flex, maybe foot or so, and begin beading. If I need more wire, I pull it out as needed.
Now, dont get sissor happy just yet! If I am all finished, I add the clasp the end I have been using to bead. Once the clasp is attached, I'm ready to cut the other end and detach the strand from the spool. At this point, attach the loose end to the other end of the clasp.
This way keeps you from dropping beads all over the floor when they slip off the opposite end you are working on.
This also will save you from wasting your soft flex. When I pre-cut a strand before beading, I often find that I have cut way more wire than I need. The extra soft flex is usually too long to do anything with and goes into the garbage...