iFixit

Once the solvent has had a chance to work its magic (10 minutes or so), use a rough-grit sandpaper (100 grit or so) to clean the inner diameter of the drum. Rinse and repeat until you are satisfied with the cleanliness of the drum.

Attach the two brake shoes and springs together. First put both springs through one of the shoes, then loosely attach the other side of the springs to the other shoe.

Apply silicone grease to the round and flat bolts on the brake drum assembly.

Be careful with this part, as the brake shoes are under load. It took me a couple of tries (and different methods) to accomplish this properly.

Carefully spread apart the round side of the brake shoes and place them through the round bolt on the brake drum assembly.

Then, spread apart the flat side of the brake shoes and place them through the flat bolt on the brake drum assembly.

The shoes should now be sitting as shown.

Place the wheel back on the axle. Make sure that the thread of the axle matches up to the thread of the wheel.

Replace and tighten the 22 mm lug nut with a ratcheting socket wrench.

Use a hammer and pair of vise grips to slide the wheel retaining pin back into place.

Follow the directions in step 2 in reverse order to reattach the brake cable.

Adjust the brake cable adjustment nut as necessary. The rear brake lever should be about 0.8" to 1.0" away from the handlebar when fully engaged.