I would say that one of the best things against OS is to wait, and punish him. Rushdown pressure game is completely overwhelemed by 5S, and sometimes 6p is interupted by 5HS. I couldn't believe it until I realized, just how quick his attacks are. The frame number must be low I am assuming, because in some cases parrying doesn't even have the potential of helping. His pressure is worst, because it can start up from a distance, before steadily, advancing closer.
So far, the only strategy I can give you for this, is to wait for an opening, and land a good
2S on him. Other then baiting out his VV, and using the Sol strategy, the only difference is that, OS can be more random then Sol. So punishing may end up a little tricky. You could lure the Order-Sol in parry, and proceed to comboing him into wallstick combos if ya want. after every f,5S TK into a Ryujin. You have to try to get the most out of an oppertunity, but you have to be smart about how you act. Its good to have one or two of the special kicks charged up. FD canceling is must, in this match-up, but be warned. One false move and game-over. But denfensive play is best for this fight IMHO.