Yup, for sure HPWM is the way to go unless you've already used those pins up, in which case you can go SPWM, but that chews up processing time. HPWM isn't "slow or fast" like Henrik says, you just change your duty cycle as quickly or slowly as you want to, you can test it with a pause loop, and then implement via a timed interrupt routine (which obviously has less overhead).