This sounds like the frustration I went through on my first boat. When I built my Coastal, I decided to glass the coaming in a two step process.

I put the kayak on its side and glassed the "top" side of the coaming. It was easy to get under the lip. When that cured, I flipped the kayak onto its other side and did that side. It worked well for me.

Take care jim

p.s. it sounds like you're real close to a first launch! Congratulations.