Shiny Pokemon Question. Growlithe.

I am new to the shiny world in capturing them.
I know about the soft resets and the rarity and ratio of finding a shiny.

My favorite Pokemon is Growlithe.
I'm currently playing HeartGold so they are usually on routes 7,8,36,37, & 48.
Yes, a shiny Growlithe don't look much more different than a regular one but having a shiny one, well, that would be really cool. Especially if it's your favorite :)

My question is since there are other Pokemon that are the grass on those routes along with Growlithe, would I still be able to find the shiny or would it take a lot longer? Should I even soft reset or just keep 'running away' and re-entering in the grass?

Thank you.

I have read that if you breed like crazy with forigen pokemon(Ex. A forigen ditto and a normal growlithe OR a forigen growlithe and normal ditto)you have a slightly higher chance of hatching a shiny.Also if you beat more than 40 of the same pokemon(Ex.Beat 40 or more Growlithes in the wild in an area)You have a slightly higher rate of finding a shiny,but keep in mind that both of these actions takes patience.Another way is trading for a shiny.Lastly theres always one last resort....Hacking the game(Action Replay).If i were you,i would want to breed or defeat 40 or more of the same pokemon to end up with a legit shiny.
Hoped this helped :)

Yes, the Masuda Method is breeding two Pokemon from different languaged games. However, the Chaining method that you mentioned is only available in games that have the PokeRadar (Diamond, Pearl, and Platinum only). Chaining 40+ pokemon using the Pokeradar will increase the chances of encountering a shiny pokemon in the wild.

The least volatile manner of encountering a shiny is through Masuda Breeding.

Spoiler: (highlight to view)

If you wait until Black 2 and White 2, there will be an Item available that greatly increases the probability of encountering a shiny pokemon.