My favorite dark cloth is made by sewing heavy black fabric to the silver material used to cover ironing boards available at any good fabric store . It is opaque, cool (reflects sun off) and waterproof.
My wife has made me two (for 4X5 & 8X10). For the larger one, she used white & black fabric with elastic for around the back standard. Works similiar to the BlackJacket as advertized on this site. She did say, though, that if I had to pay her a reasonable rate for sewing, the BlackJacket would be a better deal.
My wife made mine. She got two bed sheets - one black and one white - from walmart for $6.00 each. Folded each in half and sewed them together. Not totally light tight but, it works. I suspect that if one spent a little more on sheets, it would be plenty light tight.
I tried the "Girls Skirt" thing, but soon gave it up! The looks and side glances from by standers I got for looking up under the skirt were more than I could handle. I look enough like a suspicious character without chasing around the mountains with a girls skirt for a hat. Some how it just didn't seem proper!