Not speaking from a lot of experience but I imagine the choice of fly is much less important than the rigging and the presentation. A white/olive marabou streamer or a white/silver clouser would probably work fine. Thundercreek is another all-around style that works.
About the rigging, what I remember being told is if you use a floating line with fly rod, add a good long leader of 8 lb mono - maybe 8-10 feet? and add a couple of split shot a few feet in front of the streamer.. (I might substitute a sinking line or sink tip if I had one, I suppose).
I also hear trolling speed is considered very important for LL.. (Not sure how you manage that in a rowboat or kayak..)
Would be great if someone who's 'been there- done that' would share some of the 'how to do it' here.
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Also - I bought an assortment of 'traditional' tandem trolling streamers about 10 years ago from a guy in Maine, and I have occasionally trolled near shore from my rowing canoe with fly rod, and caught some smallmouth.. this is on Keuka but I'm sure same would work in other Finger Lakes. One advantage of these trolling flies is that they use wire to link the two flies, and some have beads on the wire, which gives them some weight to make them sink a bit deeper. Something to consider if you plan to tie some of those. Though clouser or conehead flies are probably equally if not more effective.