2007 Tacoma Head Gasket Repair Questions

Recently dove into a Head Gasket Job on a 2007 Tacoma 4.0 that has 490,000 KM on it, the truck drove fine about 90% of the time but on a cold start would puff white smoke until warmed up the truck had a rough idle and a cylinder 4 miss fire code, was diagnosed using a borescope at a shop and found that cylinder #4 had coolant in it.

This is my first time attempting a repair like this i am pretty mechanically inclined but i have a few questions i am hoping someone with a bit more experience can help reassure me.

After removing the heads and tearing down the engine i couldn't help but notice how clean everything was no sludge or anything like that looks like it was really well taken care of during its life.

After removing the heads i began to clean up the Block with brake clean and did use scotchbrite by hand carefully in a couple spots that were tough to get off (this was before i found out online that this wasn't a great idea) however i was pretty careful and didn't use it on the entire block so i still feel alright about it i've checked the block with a straight edge and everything seems to look good and the heads were sent to a machine shop for laser cleaning however i noticed i scratched up some of the machine marks a tiny bit in one spot on the block when using the scotchbrite, I can see some scratchy cloudy marks but it checked out fine with a straight edge and i don't believe i really took much metal off.

Wondering if anyone has any experience messing up like that and if they were still ok after re assembly.

Ive read online people use a copper gasket spray for head gaskets is this something i should apply or not worry about it?

I purchased a Felpro Head Gasket and was under the impression this is a decent head gasket i will be selling the truck once the work has been done but i want to make sure its a good truck for someone else to enjoy anyone have experience with the felpro head gasket?

Here are a couple photos of the Engine anyone know why some of the exhaust valves are cleaner then others something to do with the head gasket and burning coolant?

first photo middle cylinder is cylinder 4 before being cleaned up, i noticed it was wet and kinda dirty i figured that was where my leak was although didn't see any obvious failure in the head gasket.

i was pretty impressed for a truck with 490,000km what do you guys think any tips or pointers for re assembly i should know about?