we still know and use it most often as Tom and Huck did when they painted a fence

Yes, musick!...I was going to mention Mark Twain's famous scene in Tom Sawyer where Tom suckers his friends into whitewashing the fence for him, and sits back and takes credit and pay for all the work. Perhaps this is where "whitewash" gained its connotation for connivance, putting one over, slanting the truth, etc.