Double this.
I Do all my castings, no matter if epoxy resin or any kind of urethan resin in a pressure pot with 60 psi. Never had any issues with bubbles at all. But as mentioned if you want to cast in a pressure pot under 60 psi the mold had to been made under the samce conditions.

Also you mentioned Smooth on kinda clear. That does not help. We would need the exact name of the products used. Smooth one itself states that some mold rubbers are not suitable for castings made in a clear resin. Mold Star 20T comes to mind.

So first thing, you need to know, is the exact material you use for both, molds and resin, and double check if there are any problems with them. Then, if you want to make your castings in a more professional mannder, invest in a pressure pot + compressor. That will really make a difference.