I've also used the new style slug pellets for a while. I don't know if this works or is just coincidence so I have convinced myself it does, but I always scatter a few pellets around the appropriate bit of my plot n the week or 2 prior to planting or sowing, as well as afterwards.
I read on here somewhere a few years ago that the trick is use a little but more frequently, as they are a longer term solution than the old style pellets.