Lucy, you say you are in the country, that implies you have room available. I don't know how much you use, but extra room always helps. Breeders often keep one or two hens with a rooster for the breeding season and seldom have the problems many people will have you think are inevitable. One of their secrets is that they use hens and rooters, not immature pullets and cockerels. In my experience you don't need a magical ratio of hens to roosters for a peaceful flock but any flock regardless of size or ratio will not be very peaceful while you have immature cockerels. It can help when the pullets mature also if you are keeping cockerels an pullets together.
I'm not sure how you manage yours. Are they confined to a coop/run area or do they free range? How you manage them can make a big difference. Are you willing to run two separate flocks, at least one always confined if the need arises?
One issue is adding a second male to a flock that already has one cockerel in it. They are going to work out which one is boss. Sometimes that is relatively painless, especially if they are raised together as siblings or with one the dominant flock leader and the other starting out as a chick. But sometimes it can be a fight to the death, even if they are raised together. As always in anything related to behaviors the more room you have the better but even totally free range you don't get guarantees one way or the other. Even if you introduce them to each other when both are older they may work out their differences but it will probably involve more fighting, the risk is higher. So yes it is possible to add a second male to the flock, but it is an area of risk. There will probably be at least some fighting.
Another issue is that any male regardless of size is likely to mate with any female regardless of size. That happens all the time in flocks with both full-sized and bantam chickens regardless of which is the full-sized and which is the bantam. I'm assuming your Silkie is bantam, not all are. As long as they are in one flock you can't control this. As horrified as some may be at the thought, not all bantams mated by a full-sized rooster are injured by that mating. What this means is that if you want to breed pure Silkies you will need to isolate them during the breeding season or at least keep her away from the other cockerel. If you wish you can keep a few of the other pullets/hens in with the breeding pair, you can probably tell which eggs are the Silkie's by size or color.
The easy way to do this is to keep the Silkies confined into their own coop/run year around. Don't ever let the males together and don't let the Orp cockerel near the Silkie pullet. Or keep the Orp cockerel confined. Or get rid of the Orp cockerel. I don't know what your goals are or why you want the Orp cockerel, you just said you want to breed Silkies. If you want to breed Silkies badly enough you can find a way.
