Right, I'm not sure how good that will be as I've never tried it but I believe it's do-able. I suppose it's not really that important to get a nice looking weld as it will be sanded off won't it, you just want it to be well stuck.
I've a couple of pics here, a bit
**** but you get the gist...
This is the wheel arch, you can't really see but it is just a raw edge that's been worn away by the tyre, you can see where I've welded down the front edge aswell and sanded it off.

This is after I've welded a strip on the full length of the tub.

That's a full weld along the flat bit at the back, up around the arch and the little flat bit at the front.