When I say "leak" I refer to any poo that escapes. Usually for me, it leaks out from under the wafer, and then goes all over.
For skin breakdown, I use the "crusting" technique. Stoma power then skin barrier spray, let dry, repeat 3 or 4 times. Doing this usually gives my skin time to heal.
When I cut my wafer, small is better for me. The hole actually touches the stoma, making a tight squeeze. That helps me with skin breakdown.
I'm not sure on the paste, I don't use it. I'm eakin seals all the way.