I'll offer a different point of view. In my mind, using a pay and spray is only meant to get off the caked-on crud. Any residual film or leftover dirt from there can be removed safely with the rinseless wash alone. As you're aware, even diluted APC will weaken or possibly remove sealant or wax. It's the same premise as adding a couple ounces to a wash bucket for a strip wash, only on a smaller scale. In other words, any protection you add could be removed, so you're basically wasting product however often you use that process.
I recommend you spray off most crud at the wash first. Then, at home, pretreat with diluted RW 16:1 and do the RW. No impact on your sealant/wax that way, and no wasted product.
My two cents.
Here's another way to do winter washes: