Welcome to the forums LWE!
The only tips I can offer are...
1.) To check out this recent thread for herbicide conversations...
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=507007&page=12.) Consider getting a decent sized back hoe or track hoe in there and dig out your banks so that they are not so shallow. The smartweed around my pond does not get into water deeper than a foot or so. Digging your shoreline deeper will limit it's preferred living environment and remove some of the nutrient laden soils that it is currently enjoying.
3.) Physical remove is a good thing. Leaving the biomass in the pond just adds to the nutrients that promote plant life and ultimately algae growth.
In the big picture, smartweed is not anywhere near the worst plant to have too much of. My low-experience pond mind says you can spray-kill the stuff for years to come or change the environment so that they don't like it there anymore (this does not meean something else won't take it's place).
I love your pond settig and you have come to the right place for your pond questions.