The most frequent remarks regarding OTC investing I get are tied to the performance and volume of meaningful OTC stocks. People are sceptical whether there are enough stocks that can deliver positive performance and whether these are traded enough for investors to build their positions.
Below you can see an abbreviated excerpt detailing the performance of each long idea (reports are available in Old Svenda’s Manuals). The table shows that 14 stocks were up more than 20%, 10 of these had volume bigger than $0.1 million. The date of performance data is November 2018.

The summary volume table confirms the idea of investable ideas.

I have written a more in-depth analysis of the performance of OTC stocks highlighted in the manual on Seeking Alpha.
For a more detailed presentation on why OTC market is relevant and interesting see the below presentation.