This questions was asked on TKF and this is the answer that I gave, slightly modified.
I had no clue when I first heard about this technique so don't feel bad. I did my first balloon drift last year at 60 years old.
I rig like this when I want to go extra deep, sort of like a "lemon rig". If 4 feet deep is adequate I skip the balloon Leader and attach the balloons directly to the swivel. My "doubled bait leader" is never be longer than my rod so that I can pull the fish all the way to me without pulling the swivel past the tip guide. I like a doubled bait leader of about 4 feet of 12# flourocarbon.
To attach the balloons, if you are using a Cabela's #7 Brass Barrel Snap Swivels (1 5/8" long), just pull the stem of the balloon through the swivel snap.
If you are using a larger swivel, poke the swivel snap through the stem of the balloon, but not through the middle of the stem, or your line will break before the balloon tears free. A balloon improperly attached can supply an amazing amount of tension. (I have had my line broken before I ever pulled down on the fish.)
You want the balloon to pop off or tear off before your line breaks. So you may need to test your setup before you hit the water.
I like to use 2 balloons. The advantage of 2 balloons is that you will know instantly when the balloons come off because they will separate. Usually the motion of the balloons will indicate a hit but you may look away for a moment and miss it, after all the action usually happens at least 100 yards away. Also you can get an instantaneous read on the wind with 2 balloons.
3 balloons tend to overturn and tangle line.
If you tie your hook on with a Tuna knot it will leave a small tag end loop. This is a convenient place to hang your drop weight. Size your drop weight in proportion to bait. You want the bait to have as much freedom as possible without messing things up. In summer Striper fishing you want the bait to go deep, because Striper won't follow bait up to the warmer surface. If the bait is not weighted you need to make sure that some bird doesn't grab it. I caught a Heron on a drift once. (Released unharmed fortunately.)
A properly set up balloon drift will let the fish set the hook itself. This technique is used by boat fisherman on lake Whitney to get the bait away from the boat but still let the fish hook himself.
Shark fisherman do something similar.
Actually balloon fishing has many uses. I use balloons to carry baits much further than I can cast into restricted zones.
It can used to hold a bait at a certain depth some distance from the boat at anchor.
It can be used to drift ahead of or behind the boat.
If you are using a balloon as a float for a trolled bait you may want to put some water in it. This keeps the balloon from dancing, and if it pops off you could run it down and use it again.
A filled 12" balloon can be cast only a few feet but a partial filled or smaller balloon can be cast a surprising distance.
Contrary to popular myth wildlife do not eat latex balloons and they deteriorate about the same rate as an oak leaf.
There were some more questions asked and I continued with another post:
Quote Yes very much so. Thank you for the rigorous definition (and visual)
I have to say, that is very clever. So the balloon stem(s) will just pull out of the swivel hook? Sounds like a great way to fish really far away without a bunch of extra slack in your line. end quote.
Yes just pull the stem through the closed swivel snap. Suggest a pull check to make sure you don't have to much tension or too little. I think a number 7 swivel will do a good job. (Number 10 swivel is too small for a 12" balloon).
Unless you have a stout wind there will not be a lot of tension on the line, but the fish will generally set the hook itself against the balloons.
If you stick the swivel through the balloon stem avoid the middle of the stem. Obviously the closer to the edge of the stem the easier it will be to tear through. Use the TLAR (That Looks About Right) technique. You'll figure it out.
I like 12" balloons but there are some people that use 16" balloons or even bigger. 9" balloons will work if you have small baits and a good wind.
When I am lake fishing I use only 1 balloon. I use 2 balloons when I am drifting for distance.
If the Sun is out do not fill the balloon or solar heating will pop it. Fill a 12" to only 9 or 10". Actually some people use that idea to drop the bait after a drift.
5/17/09 Doing some online research I just came across and idea that makes some sense in some situations. Use a LifeSaver to drop a bait down deeper. If the "lemon rig" type is used above you could link a LifeSaver between the balloon swivel and the main swivel. This would hold the bait at the "doubled bait leader' depth (4 feet) for the drift out. When the life Saver dissolves the bait would Then sink the full rig depth (8 feet).
Bottom of the page:
http://www.fishgame.com/HowTo/ViewArtic ... ticleid=92
"According to Tim, a regular LifeSavers dissolves in 20 minutes, a mint LifeSavers in about 15"