A lot of the students I've spoken to don't have the ability to do a research rotation 3rd year because they have to do mandatory clinical rotations. If this isn't a problem for you, then you need to consider what you can accomplish.
Bench work, as you say, is hard to get going in a month. Most of my classmates did not finish their projects, let alone have anything publishable, by the end of their MS1 summers. Most of the students I've spoken to take research months during 4th year and they ID an advisor in a clinical research project. Even then, there's generally a few months of low-level prep - experiment design, etc. The research rotation is generally reserved for time-intensive task of the project (like data collection).