Much is said in the boat building forums in favour of the lowly paint scraper for fiberglass work and I finally figured out why. When well sharpened the paint scraper works very well for removing high spots, bumps, drips, runs, edges and excess glass/epoxy. My success with the scraper was initially limited, but since then it has been very helpful. The trick is getting the tool sharp and keeping it that way. In order to sharpen the scraper I clamp the handle into a bench vise. Then with a flat file (nothing fancy here, just a hand-me-down from the toolbox) held horizontal I move the file across the scraping edge a number of times. Every once in a while I remove the burr from the back-side of the cutting edge by passing the file across the back edge, holding the file flat against the blade back. Thirty seconds of attention will restore the edge allowing effective scraping with little effort. Since this is not high carbon steel, the edge dulls quickly so requires resharpening after a few minutes of work on fully cured epoxy (green epoxy, being softer is less harsh on the blade). My one caution while sharpening with the file is to ensure that all of your digits pass well clear of the blade. I once allowed my thumb to be sliced open during sharpening of the scraper.
The replaceable blades are double edged. I have reshaped one side of the blade currently in the tool so that it is curved. I used the flat file for reshaping but this could probably be more quickly done with a grinding wheel. A curved blade allows the tool to be useful in concave areas, a rather handy feature for the interior of the boat. Another tip is to take the sharp corners off of the straight scraper blade. The sharp corners, if left on, tend to catch and gouge or slice into the epoxy. To remove the corners, simply round them off with the flat file.