The MicroPitch algorithm is good for this, because it can blend three subtle pitch variations together. But I’ll bet that about 1/3 of all algorithms are capable of some kind of doubling & ambient effect.
So focus on the algorithm type that offers the most control over what’s important (to you): pitch variations, timing delays, EQ fine tuning, picking strength, modulation of the delays, etc. All feature panned positioning, so a multi-channel, multi-amp, or stereo setup helps to ‘sell’ the illusion.
I like to map the PITCH / DELAY MIX control to an expression pedal, for varying the timing in real time. Many of the preset FX below are mixed back. You may want to start at a 50:50 MIX, and adjust it from there.
An algorithm sampler:
