Loopnet is by far the most popular commercial real-estate website in the US, I've used them before and been pleased.  If you insist on a crypto sale it's likely to take you a while to find a buyer.  If you're in a hurry to sell the property you probably shouldn't put those kind of conditions on the sale.

As for brokers or real-estate agents, they're helpful finding buyers, title and escrow companies.  If you already have a title/escrow company you want to work with, and find the buyer yourself you can contract a Real-Estate Attorney to draft up the contracts.  Usually a real-estate sale contract drafted by a lawyer will cost you about $10k.  Depending on the price of the property that may be less than the commission fees charged by brokers and real-estate agents.