First things First, if you want them to blend, use your faders
if he did harmony on seperate tracks
track 1
track 2
track 3
track 4
track 5
track 6
track 7
track 8
the pinpoint THE MAIN stand out note, let's track 1
track 1-------up to guide all other vocals
track 2 ------move fader slightly down to accompany track 1
track 3-------move fader slightly to harmonize with track 2,3
track4--------slightly move, now pan left
track 5-------slightly move, now pan right
track 6-------slightly move, now pan right
track 7-------slightly move, now pan right
track 8 ------ if it's an odd note, keep centered but low
I dont know how your harmonies sound, but this is how your gonna get it to sound smooth, and as one with the leadm
with all the ones panned, ad reverb, it's not necessary to put reverb on all vocals, ((unless you want to)) but like I said, It depends on the style of music your doing: R&B, POP, COUNTRY, FOLK, I dont know ---- hope this helps you out