In reply to BarrySW19:
Lots of good advice here, this is what works for me.
As I generally don't solo sea cliffs so tend to have a partner on hand to help, we do it like like this:
Rig the ab as normal with a pair of opposing screwgate binders at the power point.
First climber abs down with the bag.
When the rope comes free the remaining climber at the top hauls up the slack until the rope goes tight - this is either due to the first climber at the bottom hanging onto the end or a snag.
Climber at the top ties off the rope and abs off, either to free the snag or end up at the bottom with minimal excess rope to coil at the base.
Empty Bag is carried back up the (first) climb by the second on their back as an empty rucksack - I find the DMM pitcher works great for this - other bags available