Well, I prefer the term "parallel" for the wiring of the resistor, since it's going from hot to ground (parallel to pickups, C-switch etc.). But you probably mean the same thing.

If you liked the "full on"-tone before, you can choose a 250k resistor. If you leave it out (infinite resistance), you'll mimic the sound of two 500k pots. The value of the resistor isn't really critical, it just shouldn't be smaller than 200k.
Let the thunder roll and the lightning flash, I'm doing alright for country trash.