Basically the way to abuse FR/LG's RNG is to catch a pokémon (for example Zapdos), check its IVs, and get the seed. Then go backwards through the RNG (using the reverse RNG formula on the seed) until you find your starting seed. I never figured out how the game creates it, but the starting seed is always going to be a 2 byte number so it doesn't really matter since the RNG rarely comes up with numbers that small (and when it does the offset is usually a giveaway as to whether its the starting seed or not). I made a program that can do this, its a simple DOS program I quickly made that I haven't had a chance to make look nice. If you guys want me to post it anyway, I can.
Continue doing this until you find a seed you land on often. Once you find a particular seed that seems to work for you, use RNGReporter to check if there are any spreads for the seed that you want. Finally, you need to correctly time the frame you enter the battle to match the corresponding spread.
This seems similar to the other RNGs (aside that the starting seed is harder to figure out), but there is one key factor that seperates it from the other RNGs: button presses on the title screen seem to influence the starting seed. So to get the seed you want you have to make sure that not only are you on the title screen for the correct amount of time, but you also press the A/start buttons the correct amount of times as well. And on top of that you need to enter the battle on the correct frame. Needless to say its quite tough.