Dwelltime is nothing else then the time the (6 or 12 Vopt) ignitioncoil need to charge.
A nornal ignitioncoil / bobine can't make multispark becaus the time to charge the coil wil be to long (2 till 4 ms)
Only racecoils can make multi spark, they don't use al the energie for one spark but this wil cost a lot of power electronics to do it.
We don't use multispark for our small engines, only big engines need multispark to burn all the petrol.
Big cilinder, lot of petrol, more sparks needed to burn all the petrol - small engines, less petrol, less sparks needed to burn the petrol.
I realy don't know why people want to have multi spark ignition, there is no petrol to burn

For CDI you don't must reduce the load time for the capacitor (1 uF / 600 Volt), you need all the time you have to load it for the best spark.