To properly seal, the silicon needs to be in thick even costs to form a barrier. The granular spec you are looking at requiring a second coat is most likely just to stick the granuals. If you put the granuals in the first coat I think you works defeat the purpose of the silicon all together. The spec you are looking at is most likely for creating a safe place to walk on a flat roof, not for aesthetics. I don’t think you are going to get a surface that looks anything like a granular cap sheet by embedding granuals in silicon epically after rain washes of excess. Don’t know how big your roof is but at 30# of granuals a sq and an extra cost of silicon the price keeps climbing.
If it was my house and I really didn’t want to tear the roof off for some reason, which I would never do, I would cement and nail new metal edge over the old one, coat the whole mess with asphalt primer and torch new cap over whole thing