This technique works for just about anything--furniture, automobiles, guitars, etc.
For large projects (cars), power sanders and buffers are helpful. But for small things, it's great. And for beginners, hand-sanding and rubbing is less likely to burn or sand though paint and clear--it's a safer route...
Hey--it's a bit intimidating at first, but really not that difficult (with the right supplies.)
This example is a vintage thin-line hollow-body guitar that needed several structural repairs....
Step 1: Supplies
1) Rags. Lots of rags.
2) Wet/dry sandpaper-- 400 or 600 grit to start, 800, 1000, 2000 to finish.
3) A sponge for a sanding block.
4) A bucket of soapy water.
5) Rubbing compound.
Rubbing compounds and fine sandpaper can be found at automotive supply, home improvement, or craft stores.
Important Note: Avoid any rubbing or polishing compounds that contain silicon. It may look pretty, but any subsequent painting will be a nightmare!
6) Jewelers Rouge (or "polishing compound")
(ible user Spokehedz indicates that block polishing compounds like Jewelers Rouge are available at Home Depot. Any real hardware store is also a good source.)