Can I do this? I have a sheet cake to do and would prefer not to cover it in fondant but wanted to be able to use my birthday impression mat.

Has anyone ever tried? Did it work? Any secrets or tips?

I was planning on filling in the impression areas with different colored buttercream.

Yes you can use an impression mat as long as you use a crusting butter cream. I usually just use a printer paper towel to imprint patterns.

I actually prefer using the mat on top of buttercream more than fondant. But it needs to be crusting buttercream.
Edna

Is it the Wilton mat? Might be a little difficult, as it's huge and floppy, but can be done. I have a small diamond impression mat that I got from gsa. It's a stiff piece of plastic and it's a breeze to use.

Perhaps, if you're not too attached to the Wilton mat, you could just cut it up into smaller, easier to manage squares.

Great! Thank you guys so much!

It seemed like it was possible but I just wanted to make sure!