If you can do simple math, you can figure it out. If you want 3% OA than the solution should contain 3 grams of OA for every 100 grams of solution. So weigh a volume that you think will be more than sufficient like a quart or litter or 1:1 syrup. What ever the wight is 3% of this total is how much OA you need to add to the batch of OA solution you will make. You need a good accurate scale for this.

If I am wrong, someone go ahead and bash me stupid but I believe this is simple. Its the insanely complicated looking formulas that make it confusing. You could simply take 3 grams of OA, 47 grams of sugar, and 50 grams of water and you would be close enough to a 3% solution of 1:1 OA syrup. You would dissolve the OA in the water (Warm) then mix in the sugar.

The garden sprayer is practical for large scale application of OA. In order to get proper application amounts it take several trials to calculate the correct amount of solution applied in a given time, etc. For a hobby beekeeper, a 60, 80, or 100ml syringe is much more practical. They can be purchased at Farm and Fleet or Fleet and Farm or probably most farm animal or Pet supply stores in the medication section.