Yes, you can certainly degas the silicone before. I know people who do it twice, once in the mixing pot and the other in the mould. If you can't degas the mould but can in the mixing pot, I would definitely recommend doing this. My models often would have pockets that would hold air if I didn't degas in the mould and in my experience doing it twice is unnecessary, if you degas twice it doesn't rise as much the second time so can reduce the likelihood of overflowing. I hope this helps
Can you partially degas the silicone before you pour it?
Yes, you can certainly degas the silicone before. I know people who do it twice, once in the mixing pot and the other in the mould. If you can't degas the mould but can in the mixing pot, I would definitely recommend doing this. My models often would have pockets that would hold air if I didn't degas in the mould and in my experience doing it twice is unnecessary, if you degas twice it doesn't rise as much the second time so can reduce the likelihood of overflowing. I hope this helps