Some people (@Fridh, among others) are working on these issues, along the lines of what you are talking about.
Until we have such a solution in place I highly suggest pinging people with commit rights on your PRs, using the PRs already reviewed thread, asking for help in IRC, and just being persistent. I have found that if you get the attention of a committer they are usually happy to help.
Keep in mind sometimes threads just go stagnant because it slips a committers mind.