The best way to attack a 3-Duko cube puzzle in the shortest amount of time is to take down the easiest sides first. The most blanks on a side is usually 4 (Diagram 1). This would be called a four-blank side. Those sides require Notations. The three-blank sides may provide some quick hits, but it is the two-blank sides (Diagrams 2-4) that should be your first approach. This is of course excluding any side that just has one blank and therefore is a gimme.
Take those two number and quickly scan the color strings followed by corresponding numbers. If there are no quick solutions, then you may consider entering Notations for those blank squares. Keep in mind, Notation placement is a time consuming process. The two-blank sides that have six or more of one color on them (Diagrams 2 – Top side) also provide a good place to start. If speed and a quick time are your goals, than knock down the small giants first.