Here's what I've done:

1. mask off the burnt area with masking tape to prevent damage from spreading too far
2. chip/scrape off any remaining brazing flux
3. sand the area with 200-grit sandpaper and blend in edge with good paint
4. spray with sanding primer (etching-primer only needed on aluminium), let dry completey, use hair-dryer to speed it up
5. remove tape and expand the area slightly so edge of primer and original paint exposed, about 1/8-1/4"
6. sand primer with 400-grit sandpaper, blend edge of primer & original paint
7. spray with paint of choice, I find black easiest to match, otherwise I can mix model-paints to match pretty well
8. remove tape and expand area again by 1/8- 1/4"
9. sand with 600-grit sandpaper to blend in edges
10. spray clear to cover up the repair.
11. remove tape
12. sand edge with 1000-grit sandpaper to blend in
13. polish with polishing compound.

This results in a good-as-new repair. You can skip some steps if you don't need smooth blended edges or perfectly matching paint.