Get a good soaking in the shower, then use a fresh blade and just take your time. I've shaved up to a week's worth of stubble without using a clippers first and it was no problem.
When I was going through my back-and-forth shaving and regrowing phase a few years back, I remember going to a barber to get shaved. I had a #1 buzz that had been grown out for a week. I was nervous as hell when the barber smeared some lather through the stubble and then took a straight razor to it. I'd expected him to use the clippers first. I thought my scalp would be in shreds, but he did a great job.