Ok boys here goes.
Since we are reserving you will have to remove the old serving. On one end of the serving you will see a ridge that runs part of the lenght of the serving that starts on one end. The ridge is the tag end of the serving material that the serving wraps over top of. Put that side to your right. Now slice the serving open along that ridge. All you are doing is removing a thin slice a little at at time. Do not use the tip of your knife. All you have to do is to completely cut one wrap and then you can unravel the serving.

Now mark the string where both ends of the serving were. Place another mark half an inch to the right of the left end of the serving so you have three marks. The mark to the right of the left end is where you stop serving with the serving tool and you start the back serve.

Put your string on your string jig and take all the slack out of the string so that there is no real tension on the string and run your serving material between the two bundles of string at the right mark. Now put some tension on the string with the string jig. I have no way of telling you how much tension but it should be about what the bow puts on and then some. Don't be shy about how much tension. I think the more the better and I haven't damaged a string yet. Don't for get that the tension put on the string when the xbow is fired is far higher than when the string is at rest.

Now go around the string once to the right of where the serving material goes through the string.

Next wrap the string towards the left over the tag end of the serving with moderate tension and then pull down to tighten the four wrappings.

Pull the tag end towards the left to take up all the slack in the tag end and tighten the first wrap.

Now wrap the serving with lots of tension. The string will twist and you should notice that the right side gets twisted tighter and the left side more loose. While wrapping apply as much pressure to the serving tool to push the wrapping to the right. You are trying to have the serving wraps applied tightly against each other. Wrap for about an inch and a half or so and stop. Now cut off the tag end. You'll find that the string snuggles into the groove of the tool which protects your project from your knife. Cut it as close to the serving wrap as possible.
I can't explain how much tension to use but experience will guide you. Use as much as you can without twisting the string to death but enough to turn the string a couple of turns.

Continue wrapping until you hit the first mark which again is half an inch from the end of the serving and stop.

While holding the serving wrap from unravelling pull out about ten inches of serving material and cut.

Now start the back serve by putting the end of the serving material over the string. I use a hook to handle the loop. You'll need ten back serve wraps.

What are you using for the serving.

Now take the tag end and lay it over the top of the serving and using the hook continue the wrap over the tag end. Keep the wrappings tight against each other. Its hard to explain but you want to wrap amost over the previous wrap to keep the rows of wrap tight against each other.