Do you mean the comfort insert? If so, I personally don't use it. I use the pump without this.
What I do, is that I tie a bandage around my balls (you can also wrap them entirely) and then pull the balls back a bit, from the inlet of the pump.
I also when I start to pump, don't use the external pump (hand pump) a first.
I first push the pump against the "fat pad"/pubic bone and when I push it against myself, I reposition it somewhat (when I haven't any high pressure) to keep the penis inside the pump in the middle. But also to adjust the skin around the pump inlet.
When I can't get any more pressure in, I attached the hand pump and simultaneously push the pump against myself, when building up pressure with the hand pump. But If I'm honest, it's a bit uncomfortable in the scrotum area. But I feel this method are mitigating the problem. But I get used to the feeling as well.
I haven't used it, but maybe you can try this:
MITYSLEEV - PENIS PUMP SLEEVE
(They have two sizes, choose the one for
Bathmate pumps).
Many people say this
sleeve works great with
Bathmate pumps.