Home: Using Exhaust & Circulating Fans to Improve Air Quality While Staying Cool
Just a couple of points to keep in mind...

1) Any exhaust fan is moving air out of the house...that means there is outside air coming INTO the house somewhere to make up for the lost air volume. Speaking only about temperature, this could be a good thing or bad depending on where most of that air is coming in.  For instance, if it is getting sucked in from your hot attic, then your exhaust fan would be making your AC work harder.  If the air is mostly getting replaced by cool air from a basement or crawlspace, it might have a cooling effect on the inside of the house.

2) Humidity plays just as important a role in your comfort as does temperature.  Moving the air in the house around helps your AC to take out more of the moisture in the house, making it seem cooler.  Also keep in mind that your exhaust fan is sucking in outside air as mentioned above...that air may have much higher humidity than what you're blowing out...so again, the AC would have to work harder to keep you comfortable.

3) Experimentation is a GOOD THING.  Ultimately it is much more important that your house feel good than to achieve some specific temperature.  Just having air moving around inside can make it feel cooler than it is.  So, if your efforts along that line are making you more comfortable with less AC, keep doing more of it until it doesn't continue to help.

4) before you buy more fans, check the CFM (cubic feet per minute) of air they move.  Many of the smaller fans simply don't move enough air to make any difference.  You mentioned "Vornado".  I have one of those...couldn't blow out a birthday candle at 2 inches away.  It just barely cools me down any if I have it blowing right on my face.  Suggest larger fans despite the inconvenience.