keymusic, you ought to get yourself across the briny and visit Jack Brown's Seaplane base in Winter Haven, Florida.....the technique for starting the engines of the cute little yellow J-3 cub is always the same, as they don't have batteries and all those modern doodahs....
You untie the aircraft from the dock. The student is sitting in the front. You step out on the float beside your student, and pull the prop through from behind. Works a treat.
In the UK, once or twice we've had to hand prop my Super Cub. I prefer to sit inside and give suggestions, while a nice tall young man (sometimes not even young, Derek Piggot pulled my prop a while back) stands in the right place, one arm behind his back (only lose one that way) and gives it a good yank. Of course there are MASSIVE CHOCKS!