To add to what EricHartman said, my understanding is that K-sorb should be added within 24 hours of K-meta. I don't know if that's mandatory though. You're fine racking onto both as long as MLF is not occurring. Like EricHartman said, if MLF is in play when you add k-sorb, you'll get a geranium smell/flavor which is not real pleasant. This is why I usually add the k-meta, and then the K-sorb - not both at the same time. The K-meta should kill the malolactic bacteria before the K-sorb is added. If you know for certain that no MLF is in play, then go for racking onto both.
When/how you add these stabilizers really depends on what your protocol is and what you're trying to accomplish. You can actually add them after fermentation is complete and in the primary vessel as you go into cold crashing. I think I heard that this may help more yeast to drop out of suspension during cold crashing, but I have not noticed this myself (that doesn't mean it doesn't happen though).
A couple of my examples I can give you are:
1 - Traditional - Ferment 6 gal to about 1.020 in a bucket and transfer the entire biomass into a 6 gal carboy to finish up. I can add the stabilizers when fermentation is complete, and I'm cold crashing before racking off the rough lees. Because you're likely to have more particles/lees/stuff in the must, you should add a bit more K-Meta as it will bind to all those particles.
2 - Any mead I'm doing secondary additions to (fruit, spices, etc.) - I may ferment to completion in the bucket. I know I'm going to be adding ingredients in secondary, so while I do want to try and rack off of as much lees as I can, I'm not to concerned about it if I'm going to be racking a few more times due to whatever I'm adding. I'll cold crash the bucket for a few days, then rack onto the K-meta, and add the K-sorb the next day. If it's where I was hoping it would be, I do my additions and go from there.
Another technique that Squatchy has discussed is adding Bentonite (dry) during the fermentation. This does seem to help more lees drop out sooner for that first racking.