First you need to have enough capital and a Clearing Firm that can locate shares to Short. Timmy Sykes was once bragging SureTrade could locate Penny Stocks to Short with a high interest rate. This is something I highly recommend you avoid doing because if you do not have a long history like other Traders with Penny, Pink, Grey, BBs you can get wiped out. I heard SureTrade allowed Penny Stock Shorting with the lowest capital requirements, please don't Short Penny Stocks because there are so many other ways to make consistent money Trading.
Just to be clear, you're talking 20 years ago right? I'm not aware of anywhere you can short penny stocks today, regardless of how much money you have.