Read about it here on a CC thread, and gave it a go.  Works perfectly for me.

Do everything you normally do for the tappits, then before you place the tappit mold on the Mexican paste......

place a single layer of Saran Wrap on top of the paste.  Cut, wiggle waggle the mold like normal.  When you lift the Tappit off it doesn't stick to Saran Wrap.  Lift the Saran wrap off the Mexican Paste and you have a perfectly cut letter right on the board.

You can use this for any brand of cutters.

Yes it works great.  Until I found this I also was frustrated with Tappits and the Wilton letter cutter.

AYes! It works:D For the first time, it works!! No mess, no stiking, no frustration. Just some pure happiness...