First, a question, then some answers.
Do you have a good test kit? Test strips don't count, nor does letting the pool store do it. It's essential, especially given the small volume of your pool. A mismeasurement can lead to overdosing, and then trying to compensate, leading to a vicious circle.
For mixing, whatever you have handy will work, as long as it's plastic. Before I was sure what finish I had, I bought a tub of dry acid. I use the empty bucket for my mixing. I guess its a gallon and a half, maybe two gallons. Small enough to handle easily.
If all you have is an empty 5 gallon bucket, use that, just don't fill it all the way.
Dry acid does contain sulfur. I don't know the exact conditions chemically to cause it, but from time to time I would get a sulfur smell. Could have been from the ornamental garlic, who knows? I prefer to not put any more in my pool; muriatic acid is cheaper anyway.
My technique: carry bucket, measuring cup, and jug of acid to poolside. Dip acid jug in pool and swish it around, in case there's any spillage in the crate stuck to the jug. If there is, you'll get a nice ring on the deck when you set it down. Ask me how I know. Anyway, rinsed jug gets set down. I scoop out 3/4 of a bucket of pool water and set it down. Then I uncap the jug, and pour the acid into the cup
over the bucket, in case of spills. Cup gets dumped, then rinsed in the pool. Jug gets capped. Then bucket gets lifted, held far over the side, and poured in near a return. Then bucket gets rinsed in the pool a few times. Then it all gets put away. It probably took longer to type it than do it.
Millions of pool owners use muriatic acid, and you seldom hear of any injuries. Mysterious pinholes in clothes are common.
Always add chemical to water, not the other way around.