Top tips for shiny hunting:
If you want a specific shiny, try MM (breeding a Pokemon with a foreign Pokemon, it raises the chances of getting a shiny), it works for any breedable Pokemon (basically, anything that isn't a legendary, Ditto or Unown). Just get a foreign Pokemon off of Wi Fi, it has to be of a different language, like German, or Japanese. Ditto works best, as it can breed with anything, but you can check egg groups to see if it's compatible (e.g. With Deino, any Dragon Pokemon should work, but the female HAS to be a Deino). Use an Everstone if you want the baby to have the same nature as the mum, and keep a Pokemon with Flame Body in your party as it makes hatching quicker.
- There is also SRing, when you save (vital!) before receiving or battling a Pokemon, it only works for starters, legendaries, gift Pokemon (e.g. Eevee, the monkeys, fossils) and Pokemon that are visible in the overworld (e.g. Drifloon, Musharna). You then click A,
then if the Pokemon isn't shiny when you either send it out, it appears on the battle screen or you check its profile, you press L, R, start and select at the same time. This takes you to the start screen where you repeat the process.
- The final method you will need to know is REing. This is running around in an area (Victory Road in your case, as you want Deino) and encountering lots of Pokemon until a shiny pops up. There's not much I can say on this one, but having a Pokemon with
Illuminate increases how often you run into a Pokemon, and having the first Pokemon you are battling with hold a Smoke Ball lets you run away more easily. The abilities Static and Magnet Pull make it more likely for you to see Electric and Steel Pokemon
Final note: For both REing and SRing, having a Pokemon with Synchronise first makes it more likely for the Pokemon to have the same nature as the one with Synchronise.
This should be a good guide to start you off! If you have any questions, feel free to VM me. =)