Today I drilled my sensor PCBs. There were only two hole sizes, 0.8mm for the TSOP IR detectors and cable holes and 0.6mm for vias.
I use high speed tungsten drill bits with this 10000rpm PCB drill I blagged in a broken state from my previous employer:
I just populated two boards, which is sufficient to complete one gun. Here are the boards, one enclosed in a transparent sensor dome:
The next step is to mount these on a headband and connect them to the gun.