There are underwater patching kits. They make it sound easy but it's tough. If you have liner material, use that. There's a really good underwater glue that out-performs the others, but I forgot its name.

I use a small rubber roller, like a linoleum roller to smooth the patch. I STRONGLY suggest you double-layer the patch. First patch the hole (the thinner patch material is fine). Then may a much larger patch to cover the patch. That way, if there's any loose edge, it still won't leak.

Can't help on the steps.