VNAV works fine, as long as you stick to the programmed route, the wind is as programmed and ATC let you descend as per your programmed profile. Otherwise you will need FL change and VS. Once you loose the VNAV path the FMC concentrates on descending the aircraft at the descent speed you set but will warn you if you won't make any height constraints.
I generally use FL change below 10,000' anyway as it gives more control when you inevitably stray from your programmed track