I haven't read this particular overclocking guide but in general when I overclock I would just increase multiplier gradually but not touch the voltage. I keep increasing the multiplier until the system is unstable and then start increasing the voltage step by step and constantly monitor my temperatures. If by increasing your voltage the CPU isn't overheating and it works with the multiplier you wanted to use in first place then you are good to go testing. Now you would start using some CPU stresstest programs to confirm you have achieved a stable overclock.
When you know what exactly is the default voltage and what is the max operational temperature for your CPU then you would know where to start and when to stop.