starter rebuild gone wrong?

I had a starter that had decreasing performance-- click but would crank slowly sometimes and if I hit it with a hammer it would crank better. It had let out some wisps of smoke from time to time (usually when I was cranking for too long trying to get the vehicle primed and to fire up. anyway, it got worse and the hammering got more to the point that if I kept hammering it actually would start to spin faster. And then event that didn't work anymore

Finally succumbed and looked into a new starter-- nearly $300. Brushes were $16 whereas a brush plate plus the 2 additional field brushes are closer to $45.

I pulled the starter and took it apart and found the brushes were at their travel limit.

After a couple weeks of teeth gnashing, I sprung for the whopping $16 online brush purchase (after local rebuilders said they don't sell brushes)

when they arrived, the brushes were slightly off on the size, so I used the flat face of a spinning cutoff wheel to narrow them to fit in the brush plate guides.

My soldering looks like Ray Charles taught Stevie Wonder who taught me.

Put it back together and bench tested it with a battery and jumper cables (and took 2 tries to get the starter solenoid installed right). It seemed to work and the bendix would actually fly out even when I didn't trigger it separately. Meaning, when the starter body was grounded with the negative clamp and I touched the starter relay with the positive clamp, the bendix would fly out and retract when removed. And when I touched the starter side of the solenoid, the starter would spin and I think the inertia was enough to make the bendix fly out some as well I believe. In hindsight, maybe that was a warning sign??)

I never bench tested it by putting 12V to the feed side of the solenoid and also triggering the solenoid with 12v. Should have.

Reinstalled the starter and hooked up the wires and went to hook up the negative terminal onto the battery and it sparked. Thought maybe the ignition switch was turned or a light was on. But that was another warning I ignored.

anyway, all hooked up and went to crank with the ignition switch and nothing. hmm. Re positioned the connections to make sure I wasn't grounding one out and noticed the solenoid was warm to touch but starter body wasn't.

Disconnect it all and tap solenoid trigger couple times and it sounds ok. tap the starter lug with 12v and it takes a couple tries but then starts to spin over the motor (even with solenoid trigger not engaged). tapped solenoid again and sounds right. starter lug and it cranks.

I start to check continuity. First, there's continuity to ground between starter body and chassis. Good.

starter continuity between ground and solenoid trigger terminal. Bad.

continuity between the 2 solenoid terminals. Bad.

When starter field wire (I think that's what it's called-- the one that comes out of starter body and connects to starter side of solenoid) is disconnected from solenoid, there is continuity between what I'm calling the field wire and ground. Bad??

With field wire disconnected from solenoid, no continuity between solenoid terminals. Good.

So did I screw up a field brush or could one of the field brush wires be grounding out against the starter case internally? Or is it likely something with the commutator (sp?) or more internal? Could the wisps of smoke previously be indicative of something amiss on the field wire/brush side of things?

Starter sounds healthy when I'm just applying 12V to the starter side solenoid terminal when field wire is connected and cranks the engine over easily. Didn't crank when I applied 12v to the + side of solenoid.

Or can anyone explain to me that I"m a dumbass and I should have just paid the $300 for a new starter?