Not really - they don't absorb water to any significant degree. Dip the brush for a few seconds, then squeeze/flick as required.
It's not necessary because synthetics don't absorb water, but you can soak one in warm water if you want to warm up the knot. BTW, yours is not a stupid question; the only stupid question is the one you don't ask.Please don't be too harsh on me but do you need to soak a synthetic brush before use or do they not absorb any water?