I've dealt with frostbite in the past. I like to clean the comb thoroughly with straight betadine/iodine for the first few days. This encourages all the damaged areas to dry up quickly and slough off faster. After the damaged areas have dried up then I will apply an ointment for protection. Applying ointment at this point just prolongs the weepy stage, which is not ideal. He is going to lose the most damaged areas, so best if it happens quickly to get it over and done with. The betadine also prevents infection.
You may need to look at the humidity levels in your coop. A well-ventilated coop should not allow frostbite to happen. Sometimes you can't help the humidity levels, but often it can be adjusted by removing soiled bedding and allowing good air flow.