I went ahead and pulled it out today, again.

I took the cover off the starter and guess what, it looks like a brand new starter. And the brushes are clean and tight.

I pulled off the solenoid and it "seemed" ok. Everything moves freely and was lightly lubed. But when I pulled out the plunger it looked like there was some debris on it so I rubbed it with my finger and it was a little gritty. So I cleaned everything up and relubed it. Put it back in and turned the key.
Still didn't engage. But I tried again and bam, fired right up. It never did that when it was cold. So I'm going to let it sit overnight and try again in the morning. Even if it takes two tries to start, its better than it was and a good indicator that the problem is in fact with the solenoid. We'll see.