Afraid of sanding MDF?

MDF is usually processed with formaldehyde. Do not sand the surface without sealing first!  The only part of an MDF surface that usually needs to be sanded before painting is the routed or cut edges.   The best way to handle that is to apply a generous coat of sealer and/or paint or gesso.  Wait until it soaks in and dries completely.  Lightly sand with fine sandpaper.  If the edge is still rough, apply another coat of paint, dry and re-sand.  The surface should be smooth.  This process will keep the dust from the MDF from getting into the air and your lungs.

We use a filler made by Elmers for all our wood creations.  Make sure the nail hole, ding, crack or whatever you are filling is free of sawdust by blowing it out with a hair dryer or canned air.  Apply the wood filler to the area and with a damp terry towel lightly wipe the excess away being very careful to leave the area filled.  Let dry and sand lightly. 

If you have a rough area such as the end of a board or a route that raised the grain, thin the filler with water to a thick soup.  Dampen the surface first and apply the filler over the area.  Let it dry and use a damp cloth to remove the excess before sanding.  Repeat if necessary.

If you get filler in an area that you just can't sand it out, use a fine pointed item (such as a nut pick, tool from a manicure set, ice pick, dental tool etc) to scrape it  or carve it out. 

Did you know that it is not necessary to seal Balitc Birch surfaces? It contains no sap, resins or icky stuff that will seep through the paint.  Just base your surface with paint, sand and apply your second coat.  It will make a very smooth surface and eliminate the time it takes to seal, wait for it to dry and sand. If you are prepping a surface for dry brushing, just eliminate the step of sanding between coats of paint and you will have a rough surface that will catch the paint just right.