As A newbie, what are "Gross Lees" compared to the rest of the gunk in the bottom of the carboy and how do you isolate just them? Should I assume that after racking to the secondary vessel, you wait until dry, then rack again into another carboy and pour the lees from the first carboy into a quart jar to further settle?
Gross lees is everything included in the first sediment-drop; fruit pieces, large amounts of dead yeast - anything that has precipitated out in the first couple days after fermentation has finished. These lees are often fluffy or chunky in appearance, and when left in the wine for an extended time, will begin to degrade, and long story short, end up causing flavors and aromas, that are definitely unwanted.
After gross lees, are 'sur lees', which are finer, more like a fine dusting on the bottom of the carboy, and these take several weeks to gather. These are mostly dead yeast, and are used (on some wine styles) for techniques like
battonage; they aren't going to harm the wine as quickly, although they can seem to put a damper on the aroma of a wine, so it's recommended in most cases to rack off of these lees often enough to limit exposure without over-exposing the wine to oxygen from repeated rackings.
And your assumption, is right on-target. When the SG has been the same for three days, I'll rack from that - usually carboy - to another carboy, leaving behind all the sediment I can; the sediment goes into a quart jar for settling.
Most times, personally, I'll run my vacuum pump pre-racking the gross lees, to get more of the solids to drop & I'll give it an hour or two to settle - just whenever I get back to it later in the same day, and rack it off the sediment then. Between the vacuum-degassing, and racking off the gross lees to another carboy, the sur lees drop faster it seems. I've also been playing with meads recently though, and they hold more dissolved CO2 for whatever reason - massive amounts of degassing to do, to get all the sediment to drop.
