94 isuzu timing belt install

I have a 94 rodeo with 3.2 v-6 and changed timing belt on it. I followed Haynes book and am confused with some of instructions. the book says to run belt from crank mark around passenger side cam keeping belt tight as you go and line mark on belt with mark on cam and cover, then around other pulleys and install on all to driver's side cam without moving cam gears. I can not get belt on driver side cam without rolling cam to install belt and the slack that they say should be on drivers side during install is on passenger side. I do not understand how they expect you to keep the belt tight on the way around. I ended up what appears to be one cog off on the belt on one cam.

Does anyone have suggestions on how to properly install timing belt on 94 3.2 engine