Waterproofing shower help
I like the &quot;tilecoach&quot; you tube method.  Foam backerboard (hydroban, keri board, wedi).
In your case where you already have the concrete board up, I'd use kerdi membrane or a different fleece membrane.
I don't trust the roll on water proofing.  You are relying on proper film thickness.  Fleece membrane is just so much more durable and fool proof.
For the kerdi system you'd use unmodified thinset and kerdi band on seams - no silicone.