Can I make a crisco/butter/powdered sugar-based buttercream ahead and refrigerate it or freeze it for use later this week? Will it crust over? How do I "bring it back" when I am ready to use it?
Yes, you sure can.
I have done both, refrigerate it and freeze it. I store it in an airtight container like ziplock or tupperware.
For use later this week, I would just refrigerate it. I have used buttercream that was frozen for up to a month in an airtight container and it was just fine.
To bring it back, I just let it sit on the counter until softened and then stir it up to a smooth consistency.
Yep, that's pretty much it! Just keep it in the refrigerator and bring to room temp before you need to use. Everything will be just fine. Don't worry at all!
Make sure you cover it forst though. Either put plastic wrap right on top of it, or my favorite...put it in a gallon ziploc bag and squeeze out all the air. I love the bags because they lay pretty flat, and don't take near as much room as keeping it in a bowl covered.
I make buttercream ahead & freeze or refrigerate lots of time. I've even pre-colored icing plugs and and froze/fridged for later use. Takes the stress out of multi-cake weekends!