Apologies if degassing has already been mentioned.
Although I haven't got to the epoxy levelling stage on my build yet, I have had a bit of experience of some resins and silicones used for mouldmaking- After mixing and before pouring resins should be degassed thoroughly. It is very surprising how much air is trapped in the liquid even after careful mixing. I don't think you can achieve the figures on the data sheets without this process. Pouring/flow and shrinkage qualities are much improved.

https://www.youtube.com/watch?v=9sN0KT-tRsY