I like using MagicSculp, which is an epoxy clay. I roll it to forma thin snake/worm, and lay that where I want the weld bead to be. Then I'll sand a tongue depressor to form a kind of curved chisel shape, which I use to press in to the snake to shape the waves in the weld. You can use water to smooth it. MagicSculp gives you about 1-1/2 to 2 hours to work with it, as it gradually gets firmer and eventually hard.