I've seen several (youtube) professional deck builders uses a track saw to make a nice cut line for breaker boards and edge picture frame boards. I got a cheap track saw hoping to do the same for about 4 cuts rather than making about 100 cuts trying to get boards to line up. I think I know the procedure (1/8" shim underneath for protection, set blade depth to bord depth, zip across), BUT I don't see how you cut the boards against solid objects that the saw cant get to because it runs into them (e.g. against the house). I don't THINK these builders remove the boards to cut, and it my case, the accent board is in there with wall flashing and butyl calk and cortex screws which will completely barrel out once removed, so I'd rather not remove the boards to make this cut.
Is there any other way to finish this cut? Only think I can think of (and looking at one of the cuts in the picture below seems to suggest) is a multitool. No one seems to make a specific composite blade for multitools but I did get a quality carbide blade). I guess if I'm really careful with the multitool I might be able to make a cleanish cut? Any other suggestions?