The best way is to have a good plan before starting and stick to it. You don't require big changes that way!
If you want to reuse a paper or board for a new painting:
- Brush all off the pastel with a medium stiff paintbrush, outside and do it gently to avoid breathing in the dust.
- Wipe with soft cloth or soft paper towel (Viva)
- You can then brush with water, alcohol or turpentine. This makes a new under painting, use as is or turn upside down for new painting
- You can wash some sanded paper or Pastelbord with more water if you want. It will not remove all the color but will give you a soft background. Colourfix paper, Wallis and Pastelbord can take a wash off. Some of the other paper will as well, but I have not done it myself.
You can use the following helpers:
masking tape or other tape - lift with the tape and use a clean piece to lift more
soft brush (when brushing beware of the dust)
erasers - brush away loose pastels first
pencilIf the pastel has filled the tooth, you can spray lightly with a fixative, dry, and add new pastel over it. Spraying will wet the pastel and darken the color so use carefully. SpectraFix recommended, no fumes, and gives soft edges. You can cover the painting with paper and just spray the area you need to fix.
kneaded erasers - lifts pastel
fresh bread - ball the bread and use like a kneaded eraser
If you have damaged the tooth and just can't fix with the above ideas you can add new surface with Art Spectrum primer. See the link below.
Ampersand Pastelbord http://www.ampersandart.com/pastel.html
Art Spectrum Colourfix paper and primer http://www.artspectrum.com.au/old/colourfix.html
Here is a post about a painting on Pastelbord that I washed off and an almost 5 minute video of me painting and fixing:
Video click on Demos and Videos on the tabs above and scroll down a short way.