As I make all my woodenware, there's always lots of sawdust around - which makes a great smoker fuel. At the end of each session I plug the spout with a wad of paper, which ensures that there's always some unburnt fuel left inside the smoker - which is then a breeze to light next time it's needed. All it requires is some lighted paper dropped in, and we're up and running in seconds.
But - this way of operating does create substantial tar build-up - so - all I do from time to time is place some shavings in the open smoker and pump away until flames start licking out of the top. Then I flick the spout almost into place, ensuring that it's kept open about an inch by courtesy of a short length of fencing wire.
By continuing to pump away, the flames created will eventually ignite the tar inside the spout which then begins to burn off. It's important to position yourself upwind, and if you should have neighbours, ensure that their washing isn't out on the line, as the dense smoke generated is very anti-social.
After the smoke has subsided, you'll be left with deposits which have the consistency of charcoal, which can very easily be removed with a few strokes of a putty knife, broad screwdriver, or any similar tool.