No transfer bar in a Smith & Wesson, but there is a hammer block. It drops dow out of the way as you pull the trigger.
Pretty sure I had it right over the firing pin. It's been a while. You have to cut it to the right thickness. Too thick and the hammer will not fall far enough to reset the trigger. The past few years I have used some high density foam rubber that was corner cushions inside the shipping box for a small freezer we got. It cushions the hammer fall enough that the firing pin barely moves. I put it over the firing pin. To test I inserted some 22 brass making sure the dent in the rim was not where it would get hit again. Dry fired A few times and checked for new dents on the brass. There were no new marks. Stuff is tough and a small piece holds up for 30-40 shots, at least
Did you try the piece of rubber you are using without making the hole in it? Seems like an unnecessary step to me.