Are you sure about this? I just checked coinmarketcap, and they are saying that the 24-hour trade volume for Bitcoin Cash is somewhere around $2 billion, which happens to be at least four times higher than the net worth of their one million BCH coins.
As said above, the volumes are not real on CMC. They collect data from exchanges without caring about how real or fake the volumes are. Better idea is to track exchanges such as Bitstamp and Coinbase for their volumes.
But it is possible that they could sell at least 25-30K coins per day and complete the process within one month without crashing the exchange rate for BCH?
I doubt that's a viable path to follow for them. 25,000 coins equals nearly $12 million, so you would have to dump a little on every exchange, but considering that most of the buy support you see on exchanges very likely comes from Bitmain and Roger, it's still not going to help much.
They will need to sell as much of their garbage through the OTC market, but who the heck is going to buy them?