That sounds like good advise.
If you are going to wash your feeders definitely use a mild soap and rinse very well.
I will say that I do not wash my feeders with soap very often during the feeding season. I wash them good with soap at the beginning of the season before I put them out and then again at the end of the season with soap before I put them away over winter. At the season's end I will also soak them in bleach to get rid of any mold spores that might be hiding in the crack and crevices.
During the feeding season, I use several bottle brushes and water each and every time before refilling. But, I do this just about every day. If you leave your feeder sitting for a week at a time before changing the nectar, chances are mold started so you will need to make sure you get all the mold which might require soap. The important thing is to make sure you rinse it all very good. Hummingbirds are tiny, the average Ruby-throated hummingbird weighs 0.11 ounces. Tiny!
Good luck with your hummingbird feeding. I don't know when they arrive your way but they typically show up here the first week of April. They're probably still down somewhere in the tropics but I'm ready to see them again!!
