Great question wish I had experience to help you but I noticed you didn't have any replies so let's state the obvious and give your thread a bumb, maybe someone experienced will see it.
Use MH light if your plants are stretching, to premote more vegative growth
Use HPS light for bud building, I would tend to just want this light I think unless the plants were stretching
Autoflower tickle my nerdy side, 24 hours of light on a flowering plant yeehaw!!