When Arrow Wood Finish is applied onto raw or unfinished wood, it is simple. The color the wood is when it is wet, is the color you will have when you finish it. When you apply over other finishes, color is controlled by the previous finish, so there are a few important steps to learn.
First, the good news, Arrow Wood Finish will bond permanently to any other finish including polyurethane and epoxies.
For minor scratches that have not gotten through the finish into the wood, we just apply light coats with extremely fine sandpaper right over the old finish, and rebuild the shine by going up to finer paper each coat. To just "dress" the finish up without removing the scratches, wipe a very light coat onto the wood and rub it dry with the palm of your hand. Usually this takes the white look out of the scratches, and brightens the finish.
Here is the major consideration in repairing existing finishes. If the wood is NOT stained - repairing it is easy. Use exactly the steps shown in the overview.
If the wood was stained before they applied the original finish that you are trying to repair, again it is relatively simple. Just be sure to check the color you will achieve by putting some rubbing alcohol on the scratch or worn area to be sure that your results will match the color of the surrounding finish. You may want to do several coats with finer paper to achieve your results rather than applying Arrow wood finish with coarser paper. The coarser the paper - the more likely you could compromise the color by rubbing off the layer of wood that contains it and making a light spot.
If the stain is in the finish rather than in the wood it is more difficult but certainly not impossible to fix. First, sand the wood where the finish is missing to about 800 grit. Then determine how close the Arrow finish will match by using rubbing alcohol on the unfinished places as discussed previously. If it matches well enough, just finish it as usual. If it does not match take an oil-based stain that matches the surrounding area and apply it to blend the unfinished wood to the remains of the finish that is still there. Allow that to dry overnight or as long as the stain manufacturer suggests.
Next, apply Arrow to those unfinished places and just rub it dry by hand. Let it cure overnight. Repeat that process 2 or three times. You have now sealed the stain in and put a thin buffer coat on top of it. If the results are not smooth enough or not the correct shine, you can apply more coats of Arrow with ultra fine paper 1000 grit and up without damaging the color.