We used to make "second wine" at home many, many years ago. I don't know the proportions but as I remember it, my Grandfather would not squeeze the grape skins. We had 50 or so gallon "working barrels" with open tops and drain holes near the botton that just had a wooden peg pounded into them with a mallet. When we went from primary (in the working barrels) to secondary (in wine barrels with open bungs), we just drained the wine out through the bottom. If we were not making second wine that year, we would scoop out the skins and press them. If we were making second wine, we left the skins in the working barrel and let all the juice drain out. Then, my Grandfather would replace the peg, dump in a bag of sugar (not sure of the size, maybe 25 or 50 pounds) and fill the barrel about 2/3 full with water. This would then re-start the process to make the second wine. I don't remember ever seeing a hydrometer or any other equipment. We broke up the cap with nothing but a piece of 2x4. Not very scientific and as you can imagine, the wine varied greatly from year to year. I was about 10 when my Grandfather died and my recollection is a little fuzzy on this.