Watco is meant for finishing furniture. It says right on the can, not
recommended for exterior use. Now, this does not mean that it would not work in this application. Their are many products on the market that people are using for other than the manufacturers intended use.

OK then. I am going to look into it carefully before I decide. I
will point out that many stains are used on exterior wood including
decks and siding. Watco probably has one too. My local Ace stocks
Watco and I intent to look into it but plan to use an exterior product
in any case.

There are many people who believe that belt sanders are made and sold for
the express intent of distroying things. On the contrary, there many
woodworkers, boat builders and carpenters (both professional and amateur)
that use them to very good effect. I am one. If you know how to handle it,
it will smooth and blend surfaces at least as well, if not better than, any
rotary tool.-

Thanks for that comment, CW. I like to believe I am in the latter
category. For sure I plant to carefully try the belt sander to bring
the top surface of the trim smooth and flush like you say. My plan is
to remove very little material, just enough to bring it flush, which
it should be in my mind.