When using the hand cylinders, it is recommended that the voltage be between 14 - 20v to properly penetrate the body. With that said, low frequencies will be readily felt and so it is advised to also check reduce amplitude < 10 kHz when in this mode.
As for the other option you inquired about, if using a boost cable, you will need to use inverse+sync which will effectively double the amplitude and squares the power. Either you can run with the extra power or you can safely cut the voltage in half and still remain in recommended ranges.
If you select Follow Out 1 and are also using the boost cable, you will need to modify the output of out 2 or the signals will cancel out and you will be left with an ineffective program. Spike+sync is also another option that when mixed with out 1 via the boost cable, will provide an advanced treatment mode.
Should you be plugged into out 1 directly without a boost cable, then Follow out 1 is normally selected; but since out 2 is not in use, it doesn't really matter.
As for how long each session should be, each frequency set's dwell time is calibrated for contact mode. Meaning that one to two applications of each frequency set you are looking at, per day, using a dwell modifier of 1 is all that it takes. Usually, you should run the same sets for 5 - 7 days.