To be honest I have never had a clue what anyone means when they say "slapping", or "jerking", or "pushing, pulling, fondling, tickling, squeezing, punching", or anything else that is said can be done to a trigger.
This is my non-professional opinion on how to build up speed in IDPA, especially if you are a total newbie:
1) Look up an example of a good, high, thumbs forward grip, and if you don't currently grip the pistol this way, change. Mechanically, it matters in terms of the pivot point and how well you will be able to control the recoil. Once you become more advanced, this will be a major factor in going fast. Do a little dry-fire and make sure your sights show only minimal movement in the process of dropping the hammer/striker. Some flinching due to "recoil anticipation" is almost completely inevitable at match speed, but you should be able to slow fire or dry fire while maintaining near-pristine sight alignment.
2) Start from zero (as far as speed goes) and make sure you CAN hit the target in an untimed format. Put paper plates (roughly the size of the zero zone) at 3, 5, 10, 15 yards (covers 90% of the targets you will see in IDPA), and fire slow deliberate untimed shots just to affirm to yourself that you can make the shot. If you can't, you should probably get with a coach/trainer and work on the fundamentals until you can.
3) After that, you can start to speed up. Gradually speed up with pairs at each range until you find the speed where you are not likely to hit the paper plate each time, while paying attention to the sight picture so you know about what you are seeing in terms of sights at each speed. Then back off 10%, or whatever is the fastest speed you can get two hits on the plate about 80% of the time.
At that point, in my opinion you are basically at your current opimal match shooting speed. If you are shooting ALL zeros, you are going too slow. If 20%+ of your total score is coming from points down, you are going too fast. I like to see about 10-12% of my total score come from points down, and when I'm doing what I should be doing it is amazing how consistently close I can get to that ratio. But anyhow... a little range time to find your personal limits can go a long way to improving your match performance.
And of course you can work on almost everything else that is non-shooting related at home: reloads, movement, draws, etc.