The hand lever and foot pedal actuate the same lever on the brake. There's no overall adjustment on the brake shoe lever, only the amount of free play in the cables for the hand lever and pedal. As stated above, the top wing nut adjusts the freeplay in the hand lever. This should be adjusted to give the lever a freeplay of 9/16" to 13/16" when measured from the end of the lever. The bottom wing nut adjusts the freeplay in the brake pedal. This should be adjusted to give you the same amount of freeplay as the hand lever when measured from the end of the brake pedal.
If the freeplay on both levers is set and the brake shoe wear indicator does not indicate worn brake shoes (as you've stated), the only other thing I can think of that would degrade your rear braking is water trapped in the drum. You can check this by pulling the drain bolt on the bottom/inside of the drum. If water comes out, then you probably need new seals.
Hope this helps.
2007 Suzuki King Quad 450 4x4 - 14" ITP SS112 wheels, 26" Bighorns, Xtreme 3" lift, RT2500 Winch, Twin Air filter, RAM GPS mount, Lowrance GPS, Plano ATV storage box, 2 - Playmate coolers and a RAM self-leveling beer holder
2010 Can Am Outlander 650 Max - 26" Bighorns, 200 watt audio tube by Sooner, BRP rear storage box
2007 Honda Rancher 420 4x4 ES (red), 14" ITP SS112 wheels, 26" Bighorns (Sold)
2007 Honda Rancher 420 4x4 ES (yellow), 14" ITP SS112 wheels, 26" Bighorns (Sold)