Several additional points: As you lay down thin squares of gold, it's naturally breaking up a little here and there, so there will be little 'holiday' spots to patch. These get patched over immediately as you go, and it all smoothes into one coat of gold. If the size dries out too much, or you can't do it all in one sitting, simply resize over the gold and when the tack is ready, do another layer, or carefully size portions and patch.
Gold leaf typically costs about $40 per 'booklet' of 25 square leaves. It's taking approximately two books to cover the panel in my demo, counting patching. *An additional note: imitation gold leaf looks nearly as nice as the real thing, and it's just about $7 per book. The only thing you must be sure to do with imitation gold leaf is to shellac over it to avoid tarnish.
Here are some online resources for gilding information and supplies:
*Best viewed with Quicktime 7 (free download)