A buffer is normally not needed if the value of the fixed resistor is <=10k and the wires are short/twisted.
Just try with a 10k resistor between analogue pin and VCC, and the FSR between pin and ground.
If cross-talk is a problem (when other analogue inputs are used), then add a 10-100n cap from pin to ground.
And/or read the analogue input twice (and thus use the second more stable reading).
Leo..