For stitching you can also just place a via anywhere in empty space outside the board, then edit it (E key) and set the net to ground or whatever you're stitching. Choose the dimensions also if needed. OK the dialog. Right click the via and make an array. Then drag and drop from the array to your board to stitch. If you need more, when you're down to 1 left make another array. Then when done delete the leftovers. (This
may require v5.) Don't forget to refill the zones (B). It also helps if you hide the fills (there's an icon for it on the left side) so you can see what's underneath, before you drop stitches all over. Don't ask how I know!
I like to set the grid a bit coarse when stitching so the vias line up - pure vanity.