One thing that does work well is to warm/heat the part up before applying the resin. And yes, the epoxy can be warmed also. We are talking warming to 100F or so. This causes the epoxy to be a bit thinner and the air in the part will be expanded and as it contracts it will pull a bit of epoxy back in.

I am not familiar with the particular formulation of epoxy you are using but, pay attention to curing temperature and times. Epoxy curing times are cut in half with every 10C rise in temperature or so. Some epoxies will not cure properly below 60F/15C.

There are many 'tricks' to epoxy and most industrial processes. One must be careful which 'tricks' they use for which process. Some were invented by the worker/craftsman and are good 'tricks' and make good sense in saving time/money and building a better product. Other 'tricks' can compromise the integrity if a project but are still used because a craftsman is stupid/ignorant/lazy or a combination of the three. There is usually someone up the command/food chain that is a least as stupid/lazy/ignorant or has a 'don't give a damn' attitude allowing that practice to continue. Management can be as sorry as labor.

Regrets for the long-winded answer but, stupid shortcuts are one of my pet peeves. Although using resin in an improper way in a mold is unlikely to cause problems, I have seen some of these 'shortcuts' destroy very expensive equipment and had them come too close to being my final thoughts in this life a couple of times.