5 lbs. of stabilizer will add about 30ppm of CYA. If you have already added 2 lbs. previously, then go ahead and add 5 more lbs. That should take you up to a reading of about 40-45 which would be a good level. You can add it either of the ways you mentioned. If you do put it in the skimmer, just keep your pump running 24/7 for the next 4 or 5 days and don't backwash the filter for about a week to be sure it has all dissolved. I add it different ways, different times. This year, I put it in the sock and put the sock in the skimmer basket and kept the pump running. The sock was empty within about 3 days.