I use expanders, soft hookers and hard pellet using pellet bands on the waggler. I've found that all of these methods work well, although you have to be a bit more careful with the soft hookers as they can come off quite easily when casting.
Cats and Dogs do a soft feeder pellet Nick in a large bag (the Monster Crab are brilliant).
The bags about 3.00 but it can be split down and frozen into about 6 trips worth.
They fit perfectly onto a round bend 16s and work fine on the waggler for casting. Good bag up bait Mucker.
The secret to keeping a soft hooker on is to use a big enough float so you are not struggling to cast.
If you are preparing a expander for the waggler pump them, then soak till they are still a bit hard in the middle, then drain and put in the fridge overnight. This method works with 6mm ringers, dynamite, skrettings, and GOT which are all about the same texture. The pellet will come off when you reel in as it softens in the water. Watch the pellet when you cast to make sure it is on when your rig hits the water.
Ive never found the need to use a soft pellet in the summer on the waggler, a hair rigged hard pellet will be fine, try wraping it in a bit of paste for extra attraction.
Just go to your local petfood wholesaler where you should be able to get a sack for about 20 or so.
Have a look at this article by md'er Top-dog. It's the dog's wotsits
In addition to this try using 2 hair-rigged soft hooker pellets instead.