It doesn't get any simpler than this. I merely add 2 ounces of Ivy Club Spice Aftershave and 1 ounce of current P&G Old Spice cologne (not the aftershave) into a bottle, shake it up, let it sit in a cool, dark place for four or five days (it needs a few days for the scents to blend properly), and there you go.
The reason I add the P&G Old Spice to this mixture is to give the scent some staying power; as I stated in my review, Ivy Club's longevity is awful, and by mixing it with real Old Spice, you'll be able to smell this for a good 4 or 5 hours on your skin, maybe more. Also, the Old Spice seems to act like a fixative for the Ivy Club juice. Finally, because there's a much higher percentage of Ivy Club in this mixture, that's mostly what you'll smell, without any of the P&G Old Spice's rough edges.
To give it an even more authentic touch, pour the mixture into an old empty glass Old Spice bottle, if you happen to have one handy. Or you can do what I do, which is decant it into one of the cool Old Spice special edition bottles you find on eBay for dirt cheap. I bought this neat lighthouse shaped Old Spice bottle on eBay for only five bucks, and it's what I use to house my brew:
How awesome is that?
Sure, this recipe might not smell exactly like Shulton Old Spice, but it's pretty close, and closer than Proctor & Gamble's Old Spice. Give it a try.