The OTC and Pink markets don't do too much in regards to attracting institutional investors. OTC has a slightly higher chance because at that point, the filings are required and the companies are held to a higher scrutiny to even be able to remain on the OTC. But, risk is still higher on OTC stocks.
It does help to attract new investors, however, because financial disclosures are now required, and the companies tend to be safer, and OTC investments are typically protected from being shell companies.
OTCQB AND OTCQX work on the same platform, but what's important about OTCQX (and premier) is that they are considered more "quality" companies, and more trustworthy. Those are the types of companies that are much more likely to end up on AMEX later on.
The exposure itself needs to be put out through newsletters and PRs, I wouldn't say it helps exposure, but it helps the friendliness and likeability of the company considering they're meeting certain requirements.