easiest way of all to break the bead of a car tire or any tire for that matter is so use a second automobile and run over the tire, but not the wheel. this works prefectly, every time, and breaks both beads at one passing.
to get the tire off, use alot of slippery soap. like degreaser stuff that makes your hands feel slimy, works great. you can purchase a set of tire irons from just about any auto parts store for $10-$20. tire irons dont have to be high quality, it is not a precision item afterall. you want to slip one under the bead, and pull it around, then slip the next one a few inches away and pull it around as well. keep doing this untill one bead is off, then work on the other bead. you CAN get by using screwdrivers, to do this you need to take small steps, like have the screwdrivers an inch apart on the bead as you work your way around the tire, i have done it before, its not fun but it is possible to use screwdrivers.
to get the tire back on the wheel, apply more soap and step on the tire in small increments around the bead, you may need to hop up and down a bit, but i havent net needed a tool to get normal car tire on, however i have never worked with heavy duty tires on a truck or somthing. just normal passenger car tires.
remember, soap is THE key to working on tires. if it isnt slippery its never going to come off, or go back on.
also, u dont need a high capacity air compressor to seat the bead, if you properly slam the tire into the ground while it is on the rim, there can usually be sufficent air pressure to get a good enough seal so that you can use any air compressor, even those dinky 12v ones. with that said, a nice large compressor with a big tank is awalys helpfull.
i personally use a set of tire irons, a 2hp compressor with 10 gal tank, another car (to run it over and seperate the bead) and a squirt bottle of degreaser.
i change my own tires because all the local morons are famous for bending wheels, even steelies!