Maidhc O Casain
Na Bith Mo Riocht Tá!
Likewise. If I'm not using a map from a PDF that already has a grid marked, I use Photoshop to add one in. I typically also go ahead and add grid labels while I'm at it, just in case there's someone who can't/won't move their own pieces around - that way they can post the coordinates and I can update the map.