First off, expect to make a mess! It gets better with experience, but initially, cocoa will go everywhere.
Expect a MEss!
After your cocoa beans have been roasted, and possibly cracked and winnowed , the next step in chocolate making is to grind them until they liquefy into cocoa liqueur. Again, I have found many pieces of equipment that just are not up to this task. To name a few, general food processors, Vita-Mix, coffee grinders (burr and blade), meat grinders (manual and electric) and mortar & pestles (we are talking alchemy here after all) are just are not sufficient to the job at hand. I have heard that a Cuisinart juicer attachment can work, but most juicers will not work.
What does work remarkably well is the Champion Juicer. It grinds and separates the husks rather nicely. It does take a few of passes, and care must be taken not rush, as the cocoa mass can become too hot, and flavor can be impacted. I have successfully done a 4 pound batch of cocoa beans in 1/2 hour. This may seem like a long time, but it really is not. After you hit a routine, you can even be cleanup and have your chocolate into your Melanger and refining within an hour.
You want to feed the nibs into the Champion (with the fine screen on now) a handful at a time, using just enough pressure on the tamper to feed the nibs in, but don't bare down - it will just overheat the motor. After two or three handfuls you should see cocoa liqueur coming out of the bottom screen, and whatever husk is left coming out of the spout. Put all of your cocoa nibs through and collect the liqueur. Don't put it through the Champion again as it does not really do anything and just makes a mess.
On the other hand, you should now pass the husk and cocoa liqueur that came out the spout back through the Champion. Each pass will allow more and more husk to be separated out until only husk is coming out of the spout. If you have winnowed well, you may not have any come out by the end.
I used to advocate mixing in your other ingredients in at this point, but since we discovered the Melanger for refining, it really serves no point to add in your sugar. If you are going to put your chocolate straight into the Melanger or simply know how much extra cocoa butter you are going to add (if you are adding any at all, it is optional), I do advise putting it through the Champion now. What it will do is free up the last of the cocoa liqueur that is in the Champion, and "flush" it out. A lot will come out the spout with more husk. Just pass it through over and over until all the cocoa butter is through the screen and "dry" husk it coming from the spout.
As for how much cocoa butter to add, there are no hard rules about proportions or ingredient but here are some rough guidelines.
Sugar content can generally runs from anywhere from 20% (i.e. 80% cocoa, a rather bittersweet chocolate) all the way to 70% sugar (Hershey's). I have found 60-65% is a nice place to start experimenting. Cocoa butter is not a necessity, just an option. It can run anywhere from 0-20%. At 20% the result may be interesting and certainly milder, but also creamier. So far, I like 0-8%.
Lecithin you will find in almost all ingredient lists of chocolate. As it says, it is an emulsifier and is often added at 1-2% of the extra cocoa butter you add. Not a lot. On the other hand, I have one test batch with 2% total added, and it definitely gave an extra silkiness to the chocolate. Aside from flavor and texture, the test batches with lecithin processed noticeably easier through the Champion Juicer. I use granular from a local health food store. I have not tried liquid but am told it works fine.
What does all this mean? Experiment! Start somewhere around 60% cocoa, 35% sugar and add a little extra cocoa butter (5%, about an ounce for the batch sizes we are working in) and lecithin if you feel like it. Adjust the recipes after than. It will still be good regardless of what proportions you use.
Once it goes into the Melanger it starts out quite the ungainly mess, and looks like it can not possible work, but Alchemy it is!