Hiya
GinoBlue, chumming is an art form in itself!! I learnt to perfect my chumming tecnique in my fishing (rod and reel) days. Too little chum and the fish simply lose interest, too much chum and the fish will stay deep down, feeding on the chum.
You have different types of chumming. a few are as follows:
Pelagics off a boat. Here you either run with your boat until you find schools of baitfish being chased on the surface by predators or you look for fish or baitfish on your echo sounder (fish-finder). Once you've found your quarry, a handfull of chopped up sardines/pilchards is thrown into the water. Some guys use throw some live-bait in with the chum as well. Pretty sure fire way to attract fish to your boat!! A trick i used was to use chopped up sardines/pilchards, bought at the local bait shop, mixed with any fish based oil. The oil creates a small slick on the water surface, allowing you to see INTO the water, much like your dive mask allows you to see under water. I normally keep the chum going at 4-5 peices every 30seconds. Works well here, but you'll have to experiment with your local fish.
Bottom fish. Some guys freeze 1-2kg blocks of fish bait/guts/old bait/etc. This they put into a mesh bag and attach it to there anchor. This works very well when there is a slight current running. Be warned though, i've heard stories of sharks grabbing the chum bag and towing the boat around!!rofl
Slight variation on the above, is to tie the mesh bag to a floatline and put it in a fishy looking area. Setting up a couple of these chum blocks allows you to have multiple spots which you can monitor.
Simpler methods are to crush what-ever bait you find in your area, like sea-urchins, snails, abalone, crayfish, etc, etc. I prefer not to use this method, as you'd be destroying the fish's habitat.
With reef fish, the smaller fish will generally appear first. Take your time and wait a bit longer. The bigger ones or even some pelagics will pretty soon come in to see what all the fuss is about.
Hope that helps!!
Regards
miles