Sorry for the silly stupid question. do i frost the cake, let it harden in the refrigerator and then decorate it ? or frost, and decorate at once?

I ask because one time I refrigerated it overnight then decorated in the morning but the BC wouldn't stick to it. Maybe because i used IMBC? I don't know. I just want to make sure i do it right this time. i'm using a basic butter/shortening, sugar recipe for the BC this time. Thanks.

What kind of frosting are you using ?

You can ice and decorate at the same time OR ice then decorate the next day. To me, it depends how much time I have. I usually ice and decorate on the same day.. Once I start, I don't know when to stop.

I work with fondant, but I crumb coat the cake, put it in the fridge, and then apply another coat of BC before laying the fondant.

Perhaps try that? I know you aren't doing fondant, but I love how the second BC coat goes on. It's not hard from drying out, but the cold cake stiffens the BC while keeping it tacky (for lack of a better definitive word!).

I never refrigerate my cakes or icing.