Best way of removing TPU filament from PEI surface?

What's the best way of removing TPU filament from PEI surface?

Rubbing Alcohol? May be messy.
Baby powder?
heating the build platform?
Putting them in the freezer?

I searched the Internet and I'm confused. Same thing with PETG.

I used to surf a lot on internet and i will ask my friends for help for solving your issue.if i come to know any of these on internet,i will forward you

Have not tried PEI, I use Kapton Tape and TPU will pull it off. I print on a cold bed and I set my Z offset a little higher than it should be when using TPU so it does not lock on so tight. PETG you have to make sure the Z offset is correct, a little high and it balls up.. too low and you will never get it off.. For PETG you can try some glue stick and run under hot water to get the glue and the part off. Good luck

tpu will stick to pretty much anything with no heating.
I've used it on various surfaces - just peels off.

You can't normally break it, so just peel.

My Sainsmart Coreception printer has glass plate. One side is smooth and other side is "dull" with what appear to be some kind surface on it. Which side is up?

both ?
One side for smooth bases and one for matt.
I'd use the smooth side for pla and flexibles and maybe the ro0ugher side for more problematic filaments like nylon and abs.
The theory (I just made up) being that when a thin layer of material shrinks - ala nylon and abs - it's a horizontal pull. So the 'rougher' side with lots of microdimples should give better adhesion for the filaments that shrink.
Essentially it's got 'tread' to give better grip.

Assuming it's just held in place with easy to remove clips and you can easily flip it over - that would make sense.

For flexibles I'd just use the smooth side and no active heating.