The reason for fill through the filter well is to ensure that there are no air bubbles in the lines that would create and airlock, or the annoying gurrgling. If the wataer level isn't too low, then adding a water via the bucket method is fine. In fact like good ol' Brewman, I too have the outside water off in the winter and if I add or do a partial drain in the winter, I'm hauling 5 gallon buckets out. IF you felt that there was a chance of creating an airlock, then maybe dumping the water into filter well
might help?
One year, I did leave my garden hose outside, and the temps were above freezing for a day, so I figured I could turn the water to the hose for a while and fill the tub that way. Wrong. There was residual water left in the coiled up hose, and although I felt it was safe to turn the spigot on, the hose was frozen and useless.
I think it would be perfect it there was a inside sink nearby the hot tub, where you could attatch an adapter to the sink faucet (folks who have water beds know what I am talking about), and run a hose from the sink to the tub. The only thing is bringing that wet hose back into the house and making sure it's drained so that it doesn't freeze if you are storing outside (Garage or shed), or if inside, just coil the hose and connect the ends to eachother so no remaining water leaks out onto your floors.
If I could design the perfect set up for my tub, inside near the exit to the hot tub, in adition to having a changing - robe -towell hamper area, I'd have a utility closet with a sink, drain, hand sprayer and cabinets.
just something to think abot for the folks who are laying out thier hot tub plans, and have the resources to do so.