Well Buk its tough making a "living" making manifolds. Ask anyone that does. I do not. I make one here and there when I feel like it. I have a day job that I don't mind going to.
With that said just remember what everyone says. Clean, clean, clean. Clean the metal, keep the tungsten clean. Everytime you touch or contaminate it STOP, regrind the tungsten and then get back at it. Everytime. No exception. Good root pass on sch 10/40 is a good practice with a cap pass is how I do it. Many only make one pass, but back purge would be a must I would think. You know the rest. Its just seat time. I would suggest getting started, to leaving the filler in the puddle and make a Z or a C pattern with the torch.
Good luck, hope to see some sick shit come out of the BukFab camp!