I will weigh in here, that you can do it alone! Sometimes, it is faster alone, I talk too much if I have company!
 
When you are learning what you want to do, you will be slower, don't put any expectations on yourself and take your time. I do not use a cone at all, I tie the feet together with string, hang them from a hook at the right height, and use a wire coat-hanger to hook a bucket of water (or dog food when I had dogs, they love it) to the underside of the beak & stretch them out. About the weight of the bird in the bucket, the bucket catches most of the blood, hose nearby to wash down the concrete patio. Let one bleed while you tie up the next one, let him bleed while you hose things and untie the first, take them both to the scald pot, which needs to be the right temp. Just do 2 at a time, then decide if you are ready to do another 2. 
Colored birds can have pin feathers that show, you might decide to let them grow out more if the first couple have a lot of pin feathers which would take a long time to make a pretty, sale-worthy bird. Lots of people do not like the texture of an older bird, sounds like you know your customers tastes and preferences. But, for my neighbor's first time with a home grown cockerel, only 12 weeks old, I told her to cook it in the crock pot -- even though I consider that just the right age to BBQ. She loved it in the crock pot! You just can't put a store bird in the crock pot and get good flavor and texture like a home grown bird has. I did not give it to her until I had aged it 3 days in the frig, so that she would not have a bad experience her first time cooking a normal chicken.

 I give them to my neighbors so that I do not get any crowing complaints about my flock. I am glad you have some folks to sell them to!