Nate, you have quite a large collection of classic cars to still think that dish soap is a suitable car wash agent.
Dish soap has harsh detergents in it (to lift grease out of your way) that are way to harsh to use on your car if you want to have any sort of wax remain on the paint for more that six or eight car washes.
Use any brand of car wash soap, and use alot of it to lift the dirt away from the finish as you wash.
Bernard