The trick to balancing on a limbwalk is that you shouldn't be balancing. By that I mean that you shouldn't be trying to stand on the limb as if it was a balance beam. Get a high tie-in well above the branch you want to go out on, try to make it 25 feet or more above the branch, the further up from the branch the better. As you go out on the limb figure out which side you can put your feet on. On one side of the branch you'll just swing off the side of it. On the other side you can plant your feet with knees bent and lean back on the rope. The branch is "between" you and your tie-in up high. Now you can work your way out. If you're worried about swing back to the trunk (you should be if your TIP is not high enough) put your lanyard on the branch and move it out as you go out. You can crouch down low and practically crawl along the side of the branch. Or you can get underneath it and work your way out on the bottom like a sloth.
You shouldn't be standing straight up on the branch, you're very close to the tipping point if you do that. Use leverage and make your walk easier, lean back and enjoy the stability.
The spider rope or adjustable double-ended lanyard is a long lanyard with a DRT system on each side. Put a biner on each end of the rope. Attach two split tails at the center of the rope, you can also use a long double split tail with a butterfly knot tied in the middle. Anchor the split tails on your center delta. To climb put the biner on one end of the lanyard over a branch, bring it back and attach to your delta. Climb as you would any DRT system. When you reach the TIP take the biner on the other side of the lanyard and advance it over the next branch. Repeat. This is "alt lanyard" climbing. It's very useful in close branched conifers and can be used in deciduous trees but is optimal for conifers.
Here's a rough drawing of what I'm describing. Many climbers install a Su Sleeve or similar flexible sleeve on each side of the lanyard to protect the cambium of the branch. One thing to watch out for is hanging a biner in a crotch if you are down climbing on the lanyard. It happens very easily. Also, when you pull a biner out of a crotch it will come right at your face, be forewarned. Climbers often use steel biners on their lanyards to make it easier to throw the end over branches. I disagree with this strategy. Aluminum biners work fine, you can put a throwbag on the biner or wrap it in a monkey fist to throw it. I watched an experienced climber take a steel biner to the face while pulling their lanyard out of a crotch. Big ouch!
-moss
