no I don't think it will slow it down. Jabbing the DE bag all out for a few rounds will do you good.

IMO, it's actually quite difficult to work on your jab. You can do push ups, but IMO you have to tuck your elbow in when doing them to try to use the same muscles in the same proportions.

you can also do chest passes with a medicine ball... again, keep the elbow down.

I also "invented" a little gadget to work the jab muscles. I strapped a harness to my elbow and a bungee cord from the harness to a low point on a wall. Then just jab as though you were shadow boxing. It works the shoulder muscles incredibly well. You'd be surprised at how much resistance bungee cord will offer, especially when doubled up.

You can also do the same thing with the strap connected to your wrist to work more the tricep area to get that SNAP.

I think somewhere in the stuck thread or the subforum is a thread I started a couple years ago showing a pic of what I came up with.