I used to be able to do that on my old Vestax, it's actually not as awkward as it sounds (providing you've cued up properly), and you benefit from not getting that really noticable short change in pitch as you try and synchronise the beats, but I've tried it on cheaper decks (Kams, soundlabs) and obviously it's not as precise.When Tony De Vit was teaching fergie he used to listen to him but if he saw him touch the plate (speed itup or slow it does) he'd make him start again... he only ever used the pitch control.
Crabbing is a method of scratching whereby you move the record back & forth whilst 'bouncing' the cross fader against your thumb with each of your fingers in turn, which creates a very fast 'cutting' effect. Pretty tough to learn, I wasn't willing to put in the hours to be honest.....