This stuff is great. Using a roller is my preferred method and for christ sake read the instructions properly.
I have only done play fields and some lock down bars.
Before applying KBS I give a light spray of acrylic satin clear coat to lock in the repaired art work . As the KBS is self levelling make sure you apply on a very level surface or it might drag when curing.
No dramas yet and still very nice, no yellowing at all.
Unsure of how it will go commercially but I know that smash repairers use this for small tough ups so need for two pack.
It is air/ moisture curing so make sure you have the right conditions and seal the unused portion with plastic wrap.

My first one was on Dr Dude back in 2013 and it is still going strong, I don't own this title any more but I know the bloke who bought it.
You need ventilation Dude. Still toxic, again, read instructions well and GOOD LUCK

Pour what you think you will use into another container and seal the KBS can immediately.
Only thin if you intend to spray, in my experience.

I had bubbles when foam rolling too! I have sprayed and no drama apart from fxxking up a new nozzle.
Paint brush I think is the way to go as it is self levelling. Just throw the brush afterwards.
I keep in original container with cling wrap under lid.
Apply on a nice moderate temp, dry day.
End of the day, just have a crack
Good luck.

You are doing it too thick, too long in between coats or in high humidity.

Unfortunately there is the problem, it is a moisture cured product.