I've never tried to buy in SF, but this strategy has always worked for me and saved a lot of money over the years. Frankly I can't understand the purpose of a buyers agent in this era, and taking 3% off the cost of a house is very substantial.
When the closing statement (HUD-1) is finally prepared, usually I can see that the seller's agent took some of the buyer's agent fee, e.g. they will end up with 4% instead of 3% in the end and the rest goes back to the seller. Since these offers usually mean more money for the seller'a agent they go to the top of the pile.
It's also important to disclose that you've purchased houses before, that you have funds, and that you are ready to close immediately. You don't need a buyers agent to tell you this.