I've been using pails for a few years now and have had excellent success with the following method. Even though the manufacturers state that you can just bring the juice to room temperature to begin fermentation, I was told to always kill the natural yeast with potassium metabisulfite (campden tablets) and use wine maker's yeast to begin fermentation. I would definitely take a hydrometer reading of the Specific Gravity (SG) to insure that there is enough sugar content but leave the ph & TA alone as these are usually adjusted when the juice is packaged. Here is what I do:
1) Open the pail and take a hydrometer reading. If you must raise your sugar level (brix), use grape concentrate (available at most wine shops). I have not had good luck by adding cane sugar. Take readings for and adjust ph & TA. Record your starting SG, brix, ph & TA.
2) Crush 1 Campden Tablet per gallon and add to juice sample taken from pail. Stir dissolved Campden Tablets into the pail of juice and let sit for 24 hours. I always resecure the pail lid during this time.
3) After Campden Tablets have been in juice for 24hrs, stir 1 packet of yeast into each pail. I also add 1/4 teaspoon of Pectic Enzyme per pail at this time. This time, either leave the cover on loosely or cover with clean cheese cloth to keep fruit flies away.
4) Once a day for the next week, stir the juice gently to insure that any fine lees or solids that may have accumulated at the bottom of the pail are mixed into the juice. This is important because it allows the Pectic Enzyme to force the solids to give up their color. The first time I made wine from juice pails I simply followed the instructions on the pail and was rewarded with a fine tasting but very light colored finished wine.
5) At the end of a week's time, take another hydrometer reading. If your SG is between 1.0 and .990 you can transfer the young wine to a sterile demi-john or carboy. Some manufacturer's say to rack the wine off the lees when the SG is 1.03-1.01 and then transfer the wine again when the SG reaches 1.0 but I find this step to be unnecessary. Since I am stirring the juice every day, the lees are not settling and racking would be a waste of time for me. Record your SG and make sure you put air locks filled with vodka (i use the cheap stuff here) on top of your vessels!
6) Let the wine sit in the vessel of your choice for two weeks. Rack the wine and discard the sediment. If you like oak flavor, now is the time to add chips (approx. 1/2# per carboy).
7) Let the wine sit for a month. Rack wine and discard sediment. Crush and dissolve in a wine sample, 1 Campden Tablet for every two gallons. Add to wine and stir. Your choice as to whether or not to add more oak chips. Good excuse to try a sample! Refresh air lock vodka.
8) Let wine sit for two months. OK to sample with a wine thief to check oakiness anytime during this period. When flavor is to your liking, rack off from chips & sediment and return to clean vessel for remainder of this two month period. Rack wine and discard any additional sediment. Crush and dissolve in a wine sample, 1 Campden Tablet for every three gallons. Add to wine and stir. Refresh air lock vodka.
9) If wine needs further settling, rack wine and discard sediment periodically as sediment is noted on the bottom. Each time crush and dissolve into a wine sample, 1 Campden Tablet for every three gallons. Add to wine and stir. Refresh air lock vodka.
10) Record your ending SG, brix, ph, & TA. Knowing how your wine reacted to the process will make your further efforts more consistent.
11) When bottling you can add potassium sorbate (inhibits further fermentation) or ascorbic acid (reduces oxidation) to help preserve your wine but I tend to stay away from chemicals other that what is absolutely necessary. I don't even use fining agents only time to settle my wine.
12) Be sure you thoroughly clean & sterilize your bottles before filling! Also, when bottling, avoid splashing wine. Introduction of air/oxygen will seriously decrease its life in the bottle.
IMPORTANT: Always keep your carboy or demi-john topped up! You can use a good quality wine of the same variety to do this or simply use some of your own stock if you have some.
I know this is supposed to be a quick reply but I wanted to share a process that I have used over and over again with much success. Are there other methods? Sure and you should try all of those that sound like they will work for you. Just be sure to record as much information as possible on your process so you know how each one worked out for you.
Salute'!