The mechanism is cheap. It's just a small length of airline tubing that can go from the tank to the bucket and an airline control valve. Should cost you next to nothing if you already have airline tubing. I've done the knot method before, and it's not terribly difficult. You just tie several knots down the line and tighten them until you're dripping 1-2 per second.
I use big office clips to hold the tube in place on the tank and the bucket.
Gently pour the contents of the bag into the bucket, and then prop the bucket up on one side where it won't tip over accidentally and make sure to keep any domesticated pets out of the room to avoid an accident. I use a book or anything else flat to prop a side up. The reason is that a bags worth of water in a bucket will be very shallow when spread across the surface of a 5 gallon bucket. By tipping it up a bit on one side, it forces the volume of the water into a corner, making it deeper. Cover the bucket if you can with a towel to keep light out as it will help lower the stress.
Get the drip line dripping about 1-2 drops per second and let it go for an hour or so. Remove half the water and let it drip for another hour. I do this twice over a two hour period. Some people do more repetitions.
I've seen accounts where people place an airstone in the water to help with oxygen exchange, but I've never deemed it necessary.
Once they are acclimated, turn the lights out in the tank and gently net them from the bucket into the tank. Keep the lights off for several hours thereafter to reduce stress.