That's how the didge looked like when I bought it. I bought it from a person in private, she had brought it some 20 years ago from a trip to Australia, played it a bit and than forgot it. It's a simple, yet good didgeridoo, probably from Eukalyptus wood. It was rough cut at the bellend with plenty of excess material at it, and layered with a simple light brown varnish. The sound was OK but due to the small bellend a little low in volume.

Step 1: Removing the Varnish

First, I borrowed a tool from a neighbor who's a carpenter. With this tool carpenters usually remove the bark from branches etc. It was perfect for removing the varnish.
You can do this step as well with a sharp and reasonable big knife, it will just take a little longer.

Step 2: Sanding the Didge

After removing the varnish I sanded the didge. I have an electric tool for such work, but you could sand the wood by hand as well. In either case start with a rough sanding paper with a grain of approx. 120, then use finer grains. My finest was 400, but you could go further.

Step 3: Widen the Bellend

In this particulary case the bellend had a lot of excess material. I used a long chisel and a wooden hammer to remove the material. This is the most complicated and dangerous step. Be careful not to remove too much wood, or you're instrument will have a wall too thin or even a crack. Thus work in little steps, removing small chunks of woold subsequently. In the first foto you see the bellend before being worked on, and in the second foto you see the same bellend after all works on the didge are finished.

Step 4: Chisel and Hammer I Used for the Bellend.

Position the chisel at a piece of wood you'd like to remove. Hold the chisel in quite a flat angle. If you hold it too steep you will remove too much wood, and either the instrument's wall becomes too thin or even cracks immediately. Use the carpenter's wooden hammer on the chisel, but work soft and cautiously.

Step 5: Hanging and Oiling

After sanding you have a number of options to finish the wood. You can either use varnish, wax, or a variety of oil products. I decided to use boiled linseed oil for the outside (I will use the same for the inside next week).

The easiest way to apply the linseed oil onto the didge is by having the didge hanging. For this purpose I made a simple application from a random piece of timber of the right size, an old bicyle tube, a random screw, and a rather large washer. The bicyle tube is put through the didge and its end tied to something high at a wall or at the ceiling. The piece of wood holds the didge (it's like the didge is balancing on the wood). Make sure that both tube and piece of wood are strong, and the washer is large enough to securly seperate tube and screw. In my first experience I didn't use a washer at all and the screw slipped through its hole through the tube, and the didge fell to the ground. Not nice.

So, once your didge is hanging securely, you can use a paintbrush and layer the wood with the boiled linseed oil. Read the instructions on the linseed oil package, they will tell you exactly how long you have to wait until you can add a second layer, and probably a third. The didge will probably suck a lot of the oil since it's raw wood now.

And you should have your floor covered with a really thick layer of old newspaper or something alike.

Step 6: Let It Dry

After soaking the wood with a couple layers of boild linweed oil your didge needs a couple of days to dry. The interesting aspect of the oil is that it will really harden the surface and make it water repellent. Check once again the description of the oil's package, it will tell you more about the product's drying time.

At the end take a piece of soft fabric and remove the oil remains.

Step 7: Optional: Construct a Mouthpiece

With most simple didgeridoos it is useful to construct a mouthpiece to make playing easier and more comfortable. I opted for pure and real beewax, but the material has it pros and cons. You'll find a lot of information online if you search for didgeridoo mouthpiece.

Step 8: Result: Enjoy Your Didge

Here's how the didge looks after the whole process. I like it much better that way than befor. Even more important is of course that the sound is improved too due to the widened bellend.