Not sure what cp100 is, but I can tell you, be careful with the magic eraser, it can remove too much, real easy.
I use alcohol,Brandy mostly...oops, thats in the glass... denatured and a rag, then, novus 2.
3-4 applications, and mostly done. then, 3 coats of tree wax.
This after any touchups.

Only use Magic Eraser on playfields you are going to put a new clear coat on.

DiamondPlate playfields from the 90s have a different topcoat, but on pre 90s games, you will remove the topcoat and now be playing on the game paint itself.

https://pinside.com/pinball/forum/topic/vids-guide-to-ultimate-playfield-restoration/page/19#post-1762257

I have been working with a lot of old EMs as of late and I have a system that works pretty well. As vid said magic eraser can remove the topcoat so I use it sparingly to spot clean the dirtiest places. Too much alcohol can also reactivate the topcoat so I use it sparingly.

After spot cleaning with magic eraser, I go over it with one coat of novus 2, then one coat of millwax as it is a great cleaner and makes the playfield shine. Then two coats of a carnuba wax like blitz and they are good to go if you are not going to do a total restore and refinish.

So does it work ok to use Magic Eraser on a spray cleared EM playfield on small spots that need paint touch up?

After painting, can you just spray new clear over the small touched up areas and have the new clear blend perfectly with the old clear?

Any tricks to that?

That is one of the hardest things to do in restoring a playfield.

The old clear (assuming it's the same brand) will be harder than the new clear, so bringing them up to the same polish without digging a hole in the new patch = near impossible.

I could be months before both clears reach the same level of hardness.

So is the only real solution to strip the playfield, and prep the whole board and spray clear over everything when there are only a few spots needing repair? Basically, re-do everything...

I clearcoated an EM a few years ago, and it wasn't until after the clear coat dried, that I noticed a few spots of red paint looked bad (I didn't paint the full section to the border - lesson learned).

The whole surface is smooth and great though, so I didn't want to re-do everything for a couple of small spots.

Looks like I will continue to live with it.