I am doing a 3D T-rex cake for this week..I have a crocodile impression mat and I actually bought a cheap faux crocodile purse at Payless and literally ripped it apart to use the imprint/fabric... ..Should I imprint the fondant once I roll it out or do it after it is laid on the cake..The purse material is soft and plyable where the hard mat is not....I always have problems with the design wearing off when I smooth out the fondant.
I feel like doing it afterwards would work best. More likely to stretch/smooth the imprint out in the process of getting the fondant on. Great idea with the purse, love it! Depending on how you normally roll your fondant out (I use Sharon's method of rolling on a silicone mat so the surface of my cake isn't exposed until it is on the cake) it wouldn't hurt to imprint it and then touch it up when it's on the cake, since it's not a really an exact design. Good luck!