I find that flaking the line presents fewer problem that coiling, even with leaving the figure 8's in.
If you need to get more oomph into the winch, stand over it with one foot on the toerail and one foot on the seat. Use your hips and your whole body weight, rather than your arms or back.
Or buy bigger winches.
Or buy longer inch handles.
Also if you are ever using an electric winch DO NOT LEAVE THE WINCH HANDLE AND HIT THE BUTTON. The handle spins at a tremendous speed. It is quite scary.
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As I sail, I praise God, and care not. (Luke Foxe)