I dont think there is one retrieve that works best. You have to let the fish tell you what the magic retrieve is going to be. Ive had fish on the iron candies by fishing a flat out retrieve, a medium retrieve, just bumping it slowly along the bottom and even on a jerk jerk stop retrieve.......
The bullets have a nice kick on slower that flat out retrieves which make them a good option in low light or not so clean water whilst the cuta casting spoons are great on a flat out high speed retrieve.
In terms of colours, and in my limited experience:
Natal North coast: glow, green glow and pink glow
Moz: Glow, chartreuse flash, pink flash and sardine
As Gerhard says, make sure you give it a lob in clear shallow water (or a biggish pool) so you know how your spoon reacts to the type of retrieve. That will give you a good idea of which retrieves impart the best action to the spoon. Also be sure to keep a mental note of what retrieve you are using especially when you hit a fish so you can easily replicate (dunno about the rest of you but its the time that I'm somewhere in dreamland with the reel handle ticking over that I get blasted... then battle to remember how I was working the spoon!!)
