Changes

Take a an overpriced train or for a more normal price bus 12 or 21 to Brussels International Airport. There are many exits at the airport. You can find one and start hitching from where cars pay their parking-ticket. A bit further down the road towards the motorway you'll find a Shell service station. Most cars here stay around the airport, but you may have luck. A final suggestion is to keep on walking along the side-road until it joins with the motorway. Cars go relatively slow here and there is plenty of room for a vehicle to pull over.