AHowdy! I did a search and found multiple threads with different options. So far I've tried a new exacto knife but that got old fast especially with the thicker boards and having to cut on both sides. Jagged edges galore.Then I got a dry wall cutter. It got blunt after a couple of uses. My next option to try would be a hot exacto craft knife. Before I waste anymore time and money, any suggestions for the best tool to use for smooth edges and a clean cut? Thanks.

AI just use an xacto knife. There is a 3-step method that makes very nice cuts. The first pass you are cutting through the top layer of paper, the next pass cut through the foam, then the last pass cut through the bottom layer of paper. No flipping over. You do need a self-healing cutting mat under I to do this method. It sounds like it takes a long time, but it really doesn't because you just put the knif back in the cut you made and follow it. As you do it more you will get faster at it. Try it on some scrap if you have any.

There ae also tolls made specifically for cutting foam core.

AI forgot to say, if you are making straight lines, you need to cut along a straight edge. It will keep the cut straight and make it easier.

If you are making circles, might be easier to just get a specialized foam core circle cutting tool.

Here is a website that sells tools. http://www.foamcoreheaven.com/cutters.html

Check YouTube. There are probably videos on how to cut foam core.

AA plain butter knife. I read it on a post here and thought no way would it work. I tried it and now it's all I use.

Thank you all for the suggestions. I'm going to try them. I think my issue with the xacto knife was that I was trying to cut the whole 1/2 in board with one go rather than in steps. I found even online, the consensus  was pretty much on the basic stuff-- use a sharp blade.