summerstorm...I've finally got it down to a science, so let me tell you what I do!!
I cut the WAFER smaller (I use Convatec, so I really just make the paper part "round" instead of square) by using the Sure Seal as a template (so I know that the seal is BIGGER than the paper part)
I do everything as usual for my change, then BEFORE I put the pouch on, I put the Sure Seal on. I don't trim the SS anymore, just peel the clear parts (both pieces) off and apply making sure I pull the big crater on my stomach flat so the seal fills in. Then I peel off the white paper and if there are any "bubbles" around my crater I can usually just put my finger on the bubble for a second and it will stick to my skin.
I think the trick to my method is that I trim the wafer paper...that way the SS will fit the first time without patching all the spots like I used to.
Good Luck...i hope this helps! I know that, for me, I would not have had such consistent wear times without it