I just installed some Cap-A-Tread vinyl stair treads. Basically, these are 5/8" thick MDF boards that wrap around existing treads and give them a new "look" because of a thin vinyl layer. The vinyl is a wood pattern that matches my floors.
The steps have an exposed side, and the Cap-A-Tread have mitered "returns" to deal with this. However, the miters aren't great, and there are decent-sized gaps on the outside corners. With crown molding, this isn't a problem as it's usually all white so a combination of caulk and paint could effectively hide any gaps. With dark wood grain, I don't really have this option.
What's the best way to hide the gap of a mediocre miter on wood-look vinyl?