You cant spin on platform pedals - it just isnt possible - you can sort of do it with toe cages, but that would be hard, until you get clipless spinning is a hard concept to conceive - try out the one legged method on a friends bike or at the LBS on something clipless and see if you can sort of get a feel for it! Once you see how different it is, you will never mash the pedals again unless you are standing on them!