There's a couple of key points to this one
First, make use of the auto-tracking function (activated by hitting RB when your reticle is over the target.) This will free you up to concentrate on driving in circles around your chosen victims.
Second, choice of tank. TDs and Artillery are possible but much more difficult to fire on the move so your best bet will be to stick to light or medium tanks. I used a fully upgraded PzKpfw III (T4 medium) to get it done but any fast medium or light tank with a heavy-hitting gun should work. Also, because you won't be as accurate on the move, having a high rate of fire and/or reload is a big help too.
Third, choice of victim. Hitting targets while you're on the move isn't easy so to maximise your chances of a kill go for the weakest members of the team - the artillery. Failing that, light tanks or tank destroyers. When possible, try to blow their tracks off to make it easier for you to keep maneuvering around them.