Working with smaller than say ¾ of a five-gallon bucket of glaze this home made tool will help. I picked my 1 inch tube up at Tap plastics online and cut the tube in a 3 pieces and made a few for potter friends as well. Drilled out some wood and JB wield epoxy it into base. Place on level surface (not like photo which is very unleveled).
Now you can add a small amount of glaze and check with your hydrometer. I usually work with large glaze amounts but this works with small amounts which many use.