If you want to use the sponges, I have a couple of suggestions.
- I bought the glycerine and sponges needed for it from Amazon and the Oxalic Acid from Home Depot (Savogran Wood Bleach is high purity OA and much cheaper than beekeeping suppliers OA).
- I cut the sponges in half to make it easier to position them in the hive
- Randy tells you to dissolve the OA in the glycerine in a small saucepan over low heat. As you don’t want the solution to get above 70°C, I didn’t do that. I used a kitchen scale to weigh out 40g of OA and 50g (= 40ml) glycerine into a small mason jar. I put the lid on and left it in a bowl of tap-hot water (not boiling, just sitting on the counter), swirling from time to time. It dissolved within a few minutes
- I put the sponges into a gallon Ziploc bag and poured the warm solution onto them. I sealed the bag and left them lying flat to soak up the liquid for an hour or two
- I used nitrile gloves over my beekeeping gloves to protect them from the strong acid solution when I put the sponges into the hives
Sounds complicated, but it really isn’t. I love the method, it works brilliantly and you can safely use it during a nectar flow. 
As for @Eva’s distance perception, I personally think that 30 miles or so counts as “not too far”. Just as Lemon Grove is “not too far” from Point Loma! Maybe I should have used Eva’s phrase “your neck of the woods” instead?? Still love ya, @Eva! 