PG and VG are both alcohols and so have strong solvent properties. Some materials (oils) are more soluble in PG and VG than in water, even soapy water. So why not just use a plain PG or VG wipedown/rinse or three, and leave the Dawn for the dishes? Stronger alcohols (from jack daniels to everclear, etc) may make the "buna" (nitrile) O-rings swell, resulting in leaking.