hi, i've been using a back pack for 4 years and love it, only 1 down side is it is heavy at first. but have a sollution put back pack on floor for the first few window's, I started out like you thinking it would be a good first step but 41/2 years later still using it, unlike the vans which i have used, with a backpack there is no hose really to get tangled up, which i big advantage.
I do office blocks big ones, golfclubs, factories show rooms and domestic and with the backpack
samuel