broadly speaking there are two types of 'granulation':
Granular synthesis processes simpler waveforms by creating clusters of grains of varying amplitude and envelope, thereby introducing new frequencies; almost a highly sophisticated form of amplitude modulation synthesis. If you wish to effect granular synthesis on single pre-recorded (or live) guitar pitches, these would be the 'simpler waveform'. 'Granulation', as the other term, often refers to the chopping up of a longer soundfile, to extrapolate existing timbres/transients, with independent control over pitch and duration. The objects you should look at are [buffer~] plus [grooveduck] or [play~]; the shortest route to window/envelope shapes is either [trapezoid~] or [curve~]. A vital object is [poly~]. Thes two types of granulation/granular synthesis are hereby achieved in the TIME DOMAIN.
Alternatively, you could look at FREQUENCY DOMAIN granulation, which provides arguably cleaner results (but do check out Cycling74/examples/sampling/granular); everyone goes here for the best examples of frequency spectrum manipulation: