1. find a place with no NPC (it's a must).
2. find a narrow patch (1 or two tiles) of grass, a piece of land without grass near narrow piece of water or a cave without NPCs.
3. hit your seed (each of these encounters have their own method) and verify it with Chatot flips.
4. Start walking to see if you can activate shaking spot before you reach 128 steps. If yes, stand in front of it, advance remaining frames using chatot flips and walk/surf into the spot. Doing this advances 1 frame, so be sure to stop advancing one before your desired frame. If not, repeat step 3 and add one chatot flip while verifying the frame. Rinse and repeat about 5-6 times. If it doesn't help, find another seed.
1. In cave, you have to count all your steps as each step advances your PIDRNG frame by 2 and each turn does exactly the same thing. (DAT REPEL) The target frame should be high for shiny, so you won't miss it by walking around the cave.
2. Making 128 steps will advance your IVRNG by X where X = number of pokemon in your party. This means the desired IVs will change, so you might want to find a seed for the frame equal to number of your party members + 1 so you can gain additional 128 steps.
3. The 128 step counter does not reset when you turn your game off. This means, that after just 1 step, the IV frame can change, so be careful or just find a seed for higher IV frame (equal to number of mons in party +1)
I hope it'll help!
Good luck, this kind of abuse is a pain in the neck, so you have to be really patient.