Finn's expression is exactly the kind of bliss he hopes he can elicit later. It should be excellent fuel for Poe's memories.

Working on his balls is good, not quite as fantastic as stroking his cock directly but still intimate and enough to make Finn squirm just a little - not enough to interfere with the blowjob, he's smarter than that, but as a way to excise some of that tension without completely letting go. It can't last very long though, not with how badly he wants this.

"Poe. Poe, I'm getting close!"