I use 1/4 watt 250v 470k resistors for that application, these guys right here:
https://www.mouser.com/ProductDetail/Ohmite/OD474JE?qs=vDwvv3Pf352tXnLpr9%2FO5g%3D%3D
Keep in mind that if you use a separate resistor for middle and neck, then when you are in position 4 (middle + neck) you'll have both 470k resistors in parallel with the 500k pot, which will give you more like 160k instead of 250k.