I've never used alcohol to spray in between my CP layers. They stick perfectly fine without it. I'm not even sure if it would work with CP the same way that it does for M&P. I've only ever used it for that purpose in M&P.
You don't have to worry about ash showing up in your layers. I've never, ever had that happen in my layered CP. Each successive CP layer makes for an ash-preventing 'cover' in and of itself.
For what its worth, this is how I make layers in CP, which actually goes rather quickly for me (I usually make 2-layer or 3-layer soaps):
-I bring my batter to emulsion and then separate the batter out into separate containers for each layer I'll be making, withholding adding any color and/or scent until right before I pour whichever layer.
-I scent and color the first layer and bring it to a med-thick trace with my stick-blender and pour immediately into my mold, making sure to bang the mold to level the batter out/make it even. I've found that medium-thick trace is a good consistency to work with when doing layers. It's thick enough so that the subsequent layers won't break through if you pour or over top in a gentle manner, and although it's on the thick side- it's still fluid enough to level/even out when the mold is wiggled/jostled or banged.
-If I'm doing a 3-layered soap, then I do the same as above to the second layer, making sure to pour or spoon the batter over top of the first layer gently/carefully so that it does not break through it. Then I even it out by wiggling and/or banging the mold.
-For the top layer, I don't have to stick-blend until med-thick trace. I can pour it whenever the scent/color is mixed in properly and it has at least reached a light trace.
IrishLass