Transom Repair Fairing

[mvhull]

Hey guys, I've been rebuilding my transom on my 1974 20'CC from the outside. Cut off the exterior skin, grinded out old wood, re-bedded new ply into cabosil poly mixture and then glued exterior skin back on with cabosil as well. Next I grinded out a 3" seam around where I cut the transom and built it back up with a combo of mat and cloth tape. My question is, what is the appropriate material to use to fair out the seam.

I read that poly resin is often more water-absorbent and since I won't be reapplying gelcoat, that could be an issue. What mixture shoudl I use or can I use a product like QuickFair. I plan on repainting only the stern for now, using Interlux Perfection. The whole bottom has never been painted and the rest of the gelcoat is in great shape.