Hi Douglas,
In spite of what 3M says, there are some products that may help de-bond the 5200 for a better cleanup. One that's been around a while is "Anti-Bond 2015" while a somewhat newer one is "Marine Formula". My experience with Anti-Bond is that is does work to a certain degree, making the 5200 somewhat soft and "gooey" but still involves a lot of scraping and elbow-grease. I have not used the Marine Formula but have talked to others who claim it is much better than the Anti-Bond. The Marine Formula is sold by Downwind Marine in San Diego who are a firm well respected by long distance cruising sailors (i.e., have enough credibility that I don't think they'd sell it if it didn't work reasonably well). Anyhow, you may want to have a look around the web to see what is being said about these products (and there may be other de-bonders for all I know) and of course you should small-area test anything like this to make sure it doesn't do something horrible to your epoxy, varnish, etc.

Hope this helps.
Steve