Just go ahead and swallow. Worrying about swallowing or fighting off the urge, is worse than just going on ahead and doing it. If you feel a strong need to swallow, go ahead and then continue with your technique as if you had never done it in the first place. The panic while die down once you get more and more used to feeling of being in SP. Just keep practicing and gaining more and more experience. Try to get a little further along in the process with each attempt.