I'm no chemist, but I believe alcohol is a water based compound. So it would seem to me that you are merely diluting your alcohol with any water left in the barrel. And for that matter your alcohol better be 200 proof (100%) or after the alcohol evaporates you will be left with... water.
I believe that WD-40 displaces water, but to where? Not to the patch if it is soaked with WD. I think your just pushing the water around.
For me I find the best results are to spend a little extra time at the end of a cleaning to run more dry patches & make sure the barrel is dry. I then finish off with some Rem-Oil. I never see rust when wiping the oil out before I shoot.