What type of potentiometer to use?
Well you can modify the linear pot to get an almost logarithmic response by adding a resistor from the CCW side to the wiper. Because of its simplicity this might be worth a try. Here's what the idea looks like: -



For the pedal circuit you need this might be ideal. It's not perfect of course but it reduces the risk of buying linear pots because these can be made "almost logarithmic by adding one resistor.

One thing to remember is that if the design calls for a 1M pot and you have a 1M resistor across wiper to CCW, the end to end pot value will change as the wiper advance towards CW. This would probably mean that you should use a 2M pot and 2M resistor.

Some experimentation is required and if you could post a circuit I'm sure better advise could be given. Pictures gleened from here

EDIT - picture of circuit attached with my best guess at log/lin: -