Visa resource name PXI instrument handle

I have different instrument that can be used as DMMs, PXI-4071, Agilent 3458A, Keithley 2000, HP 34401A. I would like to have a piece of code that is as generic as possible that can use any of these DMMs. The PXI-4071 is the odd one out because it isn’t handled by a VISA resource name. Instead it needs an instrument handle. Is there a way to have one reference to any potential DMM? Having two types of instrument reference is going to clutter my block diagram especially as my application gets larger.