I promise I'm not sarcastic when I say this, but if you buy more buckets, it's a whole lot easier. Set them up side by side. When one fills, move the syphon to the other. While they're filling up with tank water, run water into your "refill" buckets, dechlorinate, and you're good to go.
I can get two 55g's done in 20 minutes.
I spend about 2-3 hours /night 4 nights a week on water changes. On average, it's 10-12 tanks/night. Tank sizes vary from 5g to 90g.
Feeding is another matter. On frozen food/live food nights, it's a 45 minute process. On flake nights, it's around 30 minutes. I have different mixes for different species. In fact I have 7 different mixes in 7 different bags.
Funny part is, I have 10 "base feed" bags to start with that I make my mixes from.