unless you are doing a huge amount of volume during these 20-30min sessions i don't think you need a full serving of surge. I'm not sure what the actual serving rec'ds are but I imagine they provide around 20/20 pro/cho. I think half of this(10/10 pro/cho grams) would serve you fine. I would preferably taking it 15 minutes BEFORE the training session though, just to halt muscle loss. And if you are really hardcore going after the muscle gains, do the same (10/10) afterwards also.
Even if you are doing an anabolic phase, I don't think extra workouts warrant meals 4-6 hours afterwards. I guess you could use them afterwards, but I really think the amount of benefit you would get from doing P+C over P+F's would be negliligible
these answers will be kinda off because i dont know your actual stats etc.etc. but they should be good guidlines