As a pickup maker I'd like to say there is no right and wrong. I suggest 500k pots, but also point out that you can use 250k if you want a slightly warmer tone. Duncan likes that tone, but you can use his pickups with 500k pots. You sure need to with the JB! You can use 100k if you want a very dark tone.
You can use higher values, like 1M if you want the least loading from the pot when its on 10.
As far as tapers, in some applications, like mixing two pickups on a Jazz bass, linear actually works better. The reason is that you are mixing two signals, and the pickups load each other. Log taper pots are good is you are actually going to do fades, but they aren't as good for small adjustments because they jump too fast past 8 or 9. Once you are lower than that, the pickup is overpowered by the other pickup.
And different manufactures tapers vary too. I like Bourns pots a lot.