I was able to get the timing down pretty good in RE3. Spike is right in a way. Do it while shooting, but if you time it right, it's not exactly random. You can just stand there and continuously shoot, then when they're close enough, pick the right time to his the X button to dodge, run away after the dodge, then shoot again from a different angle. Then just repeat throughout the game. RE6 is WAY easier. Dodging in that game is SIMPLE, and it's a LIFE saver considering in that game if you DON'T utilize the dodge you will take hits like a B*TCH.