Back yourself into the corner and aim as shown. Hold shift, tap S, then walk a step forward and jumpthrow.

Works without tapping S most of the time, however there is a rare failure mode where you either hit your head against or get stuck pixelsurfing an invisible wall, ruining your smoke. Tapping S before pressing W causes you to slide away from the wall a very tiny amount without effecting the nade trajectory.

Normally it shouldn't leave any gaps but If thrown too short it can leave a small gap under the smoke towards the back of truck.

Works almost identically on both tickrates, video shows 128-tick trajectory.

Chains very well with this molotov.