Spot meter and base your exposure on a shadow value just like you do for 4x5. Especially since you already have a spot meter and know how to use it. Film size has no affect on metering technique.

If you use an incident meter, the best approach is to learn to use it like a Zone System user would (or a BTZS user). Meter in the shadow and find a base exposure for how you want to render the shaded values. Then meter the lit areas and find your SBR and whatever development scheme you like. This takes a little reading, but there's plenty of information out there to be had.

Personally, I'd rather have an averaging reflected meter or in-camera meter than an incident meter in the field any day...

Best,

Doremus