Dosing:
At the kitten concentration, Revolution dosing is 0.01 mL per 100 g of hedgehog. Get a kitchen scale to weigh your tiny friend. It'll be a good thing to have long-term anyway so you can monitor changes in weight as indicators of health problems.
Frequency:
The medication kills any live mites, but it doesn't impact eggs. I'm not going to look up the numbers at the moment, but I think mite-lifecycle is around 21-28 days, and the medication remains effective for 21-28 days. For very minor cases of mites, one dose is enough, but to make sure the problem is gone, most vets instruct another dose 2 to 4 weeks later. Sometimes a 3rd or 4th dose 2 to 4 weeks later is also recommended.
It seems to be that if the vet rounds up on the dose (324 g hedgehog gets 0.04mL medication), they do the longer frequency (3 weeks apart), and if they round down (324 g hedgehog gets 0.03 mL) they do the shorter frequency (2 weeks apart), but there's a lot of variation. I don't think it's critically important.
Here's the drug label if you want to double-check any of that.
Application:
Because the medication is alcohol based and absorbed through the skin, it is most effective on slightly oily skin. Do not wash your hedgehog the night before dosing, the night of, or the night after so you don't accidentally wash it off.
Use a dropper or syringe to apply the medication to your hedgehog's back -- I usually aim for between the shoulder blades where he can't reach easily. (This also means you can still wash feet & belly, just don't wash his shoulders!)
You'll notice if it helps really quickly. With my little guy, I noticed he started to feel better within a day of medication, with an increase in scratching starting up the days before the next dosage.
Decontaminating:
You also want to keep mites from hopping back on him. Replace any litter or wash liners at high temperature. Wipe down his cage, hut, wheel with a water-vinegar dilution. This is to kill or remove any eggs. You don't need to be too hugely paranoid about everything he's ever come in contact with because hedgehog mites can't live long without a fresh blood source. (For example, I didn't fret about decontaminating my rugs that he runs around on during playtime.)
Storage:
The medication is alcohol-based, so it evaporates quickly once opened. To prevent that, seal it (I put the whole vial in a ziplock bag) and keep it somewhere cool and dark (back of a drawer, in the fridge...) between uses.