I have used a simple version of FIR filter and it works very well, with no delay

Xo = ((G * Xo) + Xs)/(1+G)

where Xo is the last output from the equation,
G is the smoothing factor(0 no smoothing)
Xs is the ADC sample
you will have to initialize Xo to the very first sample.
you get very good smoothing with small (2,3) numbers for G.

ed.