I am making a first communion cake for a friend. I like the look of stained glass. I saw people using gel, but how to smooth it so you do see the lines. TIA!!!

Pipe a blob of gel into the area you want to fill, then spread it with a small paint brush.

http://home-and-garden.webshots.com/photo/2250274960053175376sbkjnS

I thin my piping gel with just a touch of tonic water. (Makes it taste better too). Then I use a #1 tip as it just wants to come out of the piping bag so easily. But by using the tip I can get into the corners very easily and with it thinned, the lines from piping go away, I dont' have to worry about catching my spatula in the frosting either, especially the "lead" lines (which I've done), and it smooths itself out. Here's one I did at Christmas: http://cakecentral.com/gallery/1896162