I use 5 gallon buckets add salt the night before, just stir it with a large plastic spoon I have. Then stir it again in morning before I add it to tank!
There are many way's. If you look at my profile I have posted pics of what I do. A powerhead and a air pump hooked to an up-lift device to equal the Ion's and always check narrow parimeters(dkh,ph and specific gravity). After a couple of mixes and it test's the same, won't need to keep testing unless you change the source of your new mix water.