Here are basic instructions for multiperson massage. These assume that people already know how to give a typical one-person massage, or at least have just received a lesson in doing so. Be aware that it is much more mindblowing with 4+ hands than with 2 hands.
* Divide the body on the table by the number of massage workers. If 2 then left/right or top/bottom both work. If 3 then divide left/right and put the extra person on either head or feet, whichever they do better. If 4 then assign one to each limb and figure out how to work in the head and torso. Fitting more than 8-9 people around one person gets difficult until the recipient is very tall.
* You can do a full-body massage in about 15 minutes this way. (With one massage worker it takes about an hour.) Generally use lighter pressure than usual because everything will come unglued at once, and too much stimulation can be overwhelming. Both rubbing and kneading are okay.
* If you're doing both front and back, start face up. Some people need a hand rolling over even with one massage worker. Most people need hands with several massage workers as they are even more blissed. Your body turns into a floppy bag of pudding with sticks in it, very difficult to move. Hands on shoulders and hips can help with the tilting and make sure nobody falls.
* Finish with the plough stroke. Use bare hands or towels as desired. Allow plenty of time as this is very awesome with multiple hands. Follow the leader -- put the most rhythmic person first and others follow about 12 inches behind. With 2-3 people it usually works best for each person to put one hand on each leg and rub all the way up. With 4+ it's usually easier for each person to do one side because you have enough to do both sides at the same time by different people. It's important to peel off to alternating sides when you reach the head so you don't cause a traffic jam. Go back to the end of the line and go again.
* If you are using massage oil and have not used towels on the plough stroke, you will need to remove excess oil. Method one: do a couple more plough strokes with towels. Method two: cover the recipient with a sheet or a big beach towel and everyone rub somewhere all at once for a minute or two. Method one is slightly alerting. Method two generally douses any brain cells that were still coherent.
* Coordination is really important. If the rhythm is off it can be quite distracting. This means the massage workers need good communication and teamwork. Try to keep the location, pressure, and pace similar. Also watch your teammates closely to avoid stepping on or bumping into each other.
* Too much talking is distracting, and this is much more of a temptation with multiple workers. See above re: teamwork. Use advance planning, body language, and observation skills.
* Constant contact is actually less important. With one person, it's vital. With more than one, the person on the table very quickly loses the coherence to track everyone around it, unless somebody does something jarring.
* The hardest part for the person on the table is that if you need to give feedback (e.g. "harder" or "softer") then you have to identify the person you're talking to somehow. Usually position will work ("lighter on the left leg") but if your workers are moving around you'll have to figure out another way. If you say "ow" or something like that then typically they will all freeze or lift off which may help. Figuring out this stuff is very hard when your brain is floating in a lake of endorphins.
* Endorphins are your friends, but they make you very stoned. Don't count on the recipient being functional after this is done. That means do the massage on a bed or close to a bed if possible. Don't expect the person to move far, make decisions, remember important bedtime routines, or otherwise use their brain for more than the simplest functions. Preferably have someone strong enough to convey them to bed and pour them into it. Most people can walk after some minutes to revive, but they may not be fully stable and benefit from someone to lean on.
* The massage workers will be very tired. You might think it would be less work because it's divided, but this doesn't seem to be the case unless someone is a professional with a lot of stamina. You pour in a lot of extra energy to coordinate things. Have a place to rest and refuel. Beverages and light snacks are good. Don't plan on doing anything else for the night, you are done, unless professional + high stamina.