As a fellow paizuri lover I’ve most definitely been pondering this captivating conundrum in the past but have honestly no clue how you’d even go about emulating a titjob/titfuck with a sleeve.
Of course there are silicone breast masturbators - but with their inherent weight, getting that kind of automated movement going strikes me as pretty difficult.
The appeal of a titjob would be the weight of them slapping your groin as they go up and down if you think about it.
To replicate the feeling of two breasts squishing on your member would be trying to push warm sand / water bags together.
So i guess the softest and bland texture you can find. Bland, since you know, boobs aren’t textured like the others. Probably easier to turn a sleeve inside out since the outside is typically smooth, at least for onaholes.
The thicker it is the better probably. For both weight and close to replicating the feeling.
Not sure on tightness, but that could play a factor. Probably see about tightening the grip on the overall sleeve rather than finding the tightest hole. Hell you could probably make a belt system that can loosen or tighten.
And open hole instead of close hole, just have a bag over the opening to catch it.
If you can’t find a thick open hole one, just make a hole in a close hole.