Just don't use too much cash, lest you run afoul of banking regulations or become a victim of civil asset forfeiture.
Also interesting that a federal agency would be on board with anonymous monetary transactions.
Don’t hold too much cash. That single-handedly neuters the latter. Unless you’re spending $10 to 100k a month, banking regulations won’t give you an issue. (Below, you’re innocuous. Above, you’re big enough to find a bank that gives a fuck.)
To the point of anonymous cash transactions, I strongly suspect there are ways to acquire cash in a way that the bills which are used in a given transaction aren't necessarily traceable to the individual who made the transaction. I've heard mention of such tactics but never tried to put them into practice because I don't care enough (in most cases) to make it more than theory.