The configuration of the controls found on the Barber Half Gainer is pretty unique but it's still pretty easy to figure out how to use everything. Each of the two channels has almost the same make up, with controls for gain and volume for each, but then the first channel has a knob for midrange while the second has one for general tone. This allows you to get pretty different sounds between the two channels, which can be switched between with the button on the right while the button on the left is to engage or disengage the pedal altogether. I haven't seen a manual for this pedal...
The Barber Half Gainer is a definitely a versatile little pedal between the two channels. I like it best for overdrive sounds that aren't too overpowering as I believe that's where this is best suited. It can definitely give you some pretty gnarly distortion if you turn the gain up, but I like it when it doesn't break up as much. It's great that you've got two slightly differing channels here as it really adds to what it is capable of. Use this guy as a boost or full on overdrive and you're bound to have some nice tones happening.
For anyone looking for a flexible overdrive at a reasonable price, the Barber Half Gainer is something you should be aware of. While you can find cheaper pedals that should sound pretty good, the key here is having the two independent channels, as it's really like having two overdrives in one. While I don't know that it would be my personal first choice, it's still a great pedal that should be investigated upon for anyone interested in two channel overdrive pedals.