Our company considers testing for the presence of, or measuring the level of voltage at the MCC to be classified as "Testing" or "Diagnostic". In which case we reduce the PPE requirement to : Calorie-rated Arc-shield. 6 ounce Nomex clothing. Safety glasses. Heavy-duty leather gloves.
The only consideration given to the type of voltmeter is that it be "single function". This way you can not have it on the wrong function. I have a Tegam 125 Voltman, and interestingly, it shows no category rating. I'll check the paperwork.
If there is any 480 exposed in the bucket you are working "on or near" 480 and the hood is required. If you short out the 480 to ground or phase to phase with the probes the combustion by-products will likely be inhaled. This is the main cause of death or severe injuries in this scenario.
Start with 2-220.127.116.11 to see how to identify the required PPE. This section details the two ways to identify the required PPE for a task.
The first is as you suggested, find the task in Table 3-3.9.1 of NFPA 70E-2000 and note the hazard/risk catagory. Then go to Table 3-3.9.2 of NFPA 70E-2000 to find the PPE required for that task. This is a general table and I can see where some instances are conservative and others may be inadequate. It all depends upon the available fault current and the overcurrent device and operating time that is protecting the circuit.
The other way is to calculate the incident energy available based upon a selected working distance. The FR clothing and PPE used must be rated for this amount or higher value of incident energy.