I use the same sequence whenever for straight line blasting (1) or on jibe exit (2): pumping the sail to start the planing with both feets on the median line of the hull, insert front foot into front footstrap, pump the sail again, hook in and insert back foot into back footstrap.
http://www.youtube.com/watch?v=pbsdR59Ogcs (1)
http://www.youtube.com/watch?v=HU4YnWEc6nc (2)
In super overpowered conditions, I usually do the waterstart hooked in and with both feets footstrapped, no matters the board and sail size.
I would avoid to footstrap the back foot first because it's super easy to either spin out or stall the board speed while pumping the sail and starting the planing with an unwanted excess of back foot pressure.
Cheers !