I really like the Black & Decker GrassHog. The auto-feed system works very well. When Black & Decker pre-wound GrassHog spools were 5 for $11, I thought that was OK. When they became 3 for $9, I was concerned. I stopped throwing the empty spools away. When they became 2 for $10, it just made me angry. That is just a rip-off.
If you hand-wind them, the work is tedious, and if you don't take your time and wind very neatly they won't work. A sloppy wind results in line getting caught in the machine and it won't feed properly.
For about the price of 4 or 5 pre-wound spools I got a huge 1800 ft spool from Amazon.
At the hardware store I bought a threaded rod, 2 nuts, 2 washers, and a wing nut. I had a power drill already. This process will actually pay for itself, including a really nice power drill, after just a few uses.