Amber,
The best way to start is at home. Keep working with Dubh. He will need to neck-rein to participate in most games since you will have a spear or sword in one hand. Also you will need to introduce him to the sword and spear. Do this on the ground first. Wave them near him until his accepts this strange activity then work up to waving them close to him (make sure you don't accidentally hit him!) You should also be able to stroke him with the weapons anywhere on his body. When he accepts all this calmly, then move on to doing this while mounted. After that, introduce him to the various equipment used in the games (reeds, Saracen heads, rings, etc. ) If you plan on using a period costume on him, you will need to introduce him to that as well, especially if it is full barding with lots of flapping cloth. Dubh will also need to be accustomed to loading and hauling.
Where is Smythekep? I am in the Shire of Ardanroe which is near Shreveport, LA.
Find out if there are any fellow SCA equestrians near you that you might be able to practice with.
Melisant of Exmoor
Melissa Erlund