If you use a multi turn pot, use the little square ones with the screw adjust on top. Not the long skinny ones with the screw on the end. The latter type uses a helical element and it’s wiper can’t conduct DC current (even uA can cause trouble over time). The square ones are a standard single turn type inside that is geared down. The element/wiper interface is comparable to a single turn thumb adjust pot and is more robust. You do NOT want your bias pot getting intermittent years down the road.