2) Take a box and mount two jacks in it. It won't need to be powered, it's passive. Then take a 250k audio-taper (logarithmic) pot (you may have to experiment with the pot's resistance value) and wire one of the outer lugs to the input jack's tip, the middle lug to the output jacks tip, and the other outer lug to ground (the sleeves of both jacks). Then mount the pot in the box and slap a knob on it. Use it first in line to decrease your signal before it hits your FX chain. If you want the pot to turn the other direction to decrease signal (you feel the turning is 'reversed'), then switch the outer lugs.
Simplest DIY ever