You could go down to two cross and still get a stiff and good wheel, that would make your search much easier. To get the "dish" in the rear wheel, you need two lengths of spokes. and as a "newbie" I would not use any other than what calculations tells me too. Rear wheel not different to the front, other than you are lasing with two spoke lengths, that is what makes the rim center more easily. There are many ways to lace up a wheel, I for one lace both sides at the same time, others do only one at the time. I´ll see if I can´t find a video the I think does it a good way.