The right foot, also get yourself a book on how best to use an expression pedal, as used incorrectly it will make the music sound worse. (General rule of thumb, a nice gentle smooth flowing movement, Do not pump it)
You can also purchase Expression pedals with kick switches on each side, and use these switches for sustain, rather then having a separate Sustain pedal.
Hope this helps.

Bill
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English Riviera:
Live entertainment, Real Ale, Great Scenery, Great Beaches, why would anyone want to live anywhere else (I�m definitely staying put).