For 15 years or so (until I mostly stopped playing vinyl, basically), I was pretty religious about using a Discwasher according to instructions. Clean brush--the original one, with superfine directional bristles--in good condition. Spread out 2 or 3 drops of fluid across the leading edge. A couple of rotations with that edge, applying the mildest pressure. "Roll" the brush slowly for a few more rotations. The advantage of the system was that you applied the liquid to the brush, not the record, and unless the record was super-dirty to begin with, that was enough to loosen and scoop up anything off the surface and out of the grooves (and then lift the remaining damp off the surface before it dried). I never saw or heard evidence of any residue.
A few years ago, when I started spinning vinyl again occasionally, I scoured the web (you've probably looked in the same places: Hoffman, Audiokarma, Audiogon, Vinyl Engine, the ARSC list, etc.) for homemade replacement recipes. At that point RCA, the most recent owner of Discwasher, was still selling both fluid and brushes, but the brushes were crap. Opinion was divided on the D4+ fluid, as that seemed to contain perceptible, by which they seemed to mean "smellable," amounts of isopropyl alcohol. (People who claimed to have chemically analyzed previous formulas--D2, 3, & 4--said it was 99% distilled water and 1% undenatured ethanol--not rubbing alcohol, with a trace amount of "surfactant." Home-brew recommendations for the surfactant: a drop or two per gallon of Dawn dishwashing liquid or Kodak "Photo-Flow." Many say you don't need need alcohol at all.) A poster on one site claimed that Science magazine had once analyzed D3 and found that it was "97% distilled water, sodium azide (to kill bacteria in the grooves), ethyline glycol (the cleaner), and a surfactant (to reduce surface tension)." So in principle there could be some residue over years and years, especially if you weren't careful about quantities and procedure. But in that case you could you just wash the record with distilled water, a little Dawn, and a soft cloth, and then rinse it with distilled water.