I record with myself all the time too, Normally i make at least three, one lead, two choir, sometimes I like to make also weird things like at the end of "NIGHTMARE"
http://myspace.com/priscillahernandez
the easy way to harmonize for me is with less like in "away"
youtube.com/yidneth
Right now in my second album i'm approaching a little bit of more "symphonic classical choir" in which i'm making the mimic of voices different than mine (children like, very low tone, and very high pitched, in at least 14 layers and very softly in the back of the mix which gives the feeling of a choir there) and then the lead and main harmonies on top smile. Have done successfully a couple of songs, but it's not perfect yet, now all i need (for these so heavily with myself is to find a few volunteering different voices on top and i think i'll have a real choir feeling )

Priscilla Hernandez singer-songwriter
http://www.yidneth.com
New album at:
http://theunderliving.com