If he is having cyano issues he has another problem in his tank that he needs to take care of other than needing more carbon sources. I would nail down whatever is causing the cyano first instead of overloading his tank with bacteria and a super complex dosing regiment. Cyano isn't a rare disease that tanks randomly get for no reason, its almost always a problem from the setup or maintenance. It could be flow, water quality going in, not enough WC's, heavy feeding, long light period, ect..... And yes a skimmer, more importantly an oversized one is a must for carbon dosing.
I seen a few in nano reef that were sugar dosing. The main thing I was pulling from the threads there about it was that a little goes a very long way in small tanks and they are extremely volatile to changes in dosing. Things go bad very quick with a small water volume.
Also, a quick fix for nuicance bacteria would be some small doses of peroxide in the tank for a week or two. Should help clear it up while your working to find the problem, won't create complexity in the tank from carbon dosing, and will make the dosing regiment and testing easier.
