It appears that there is no particular way of getting a shiny Pokemon, regardless of training points. Apparently these little fellows are extremely elusive and finding one has odds of spotting one in 8,192 battles.
These odds can be improved by getting the pokeradar. The pokeradar is used by pressing the button while standing in the grass. This will cause the grass on certain tiles to shake. Going to the tile with the grass shaking is guaranteed to bring a battle.
Different pokemon will cause the grass to shake differently when the pokeradar is used. A common Pokemon, for instance, will create just a simple rustle. Rare Pokemon will cause the grass to to give just a quick shake, while shiny Pokemon will make the grass shine.
It is possible to chain the Pokemon located in this way by defeating each one spotted. After each defeat, the pokeradar will go off again and it is necessary to go to the next tile. As the chain increases, the chances of getting a shiny Pokemon also increase.
The pokeradar is obtained by talking to Professor Rowan after the Sinnoh Dex has been completed. This means all the Pokemon in the Sinnoh region must have been caught. A list of
Sinnoh regional pokemon can be found at bulbapedia. Completing the Sinnoh Dex will unlock the National Dex.
Using cheats may cause problems, as one user found out. After using a cheat to get the national dex, Professor Rowan would not hand over the pokeradar, but only comment on the amount of pokemons in the world. In order to get the National Dex and get Professor Rowan to hand over the pokeradar, the Sinnoh Dex must be completed the legitimate way.
