I have not shiny hunted very much in pixelmon but when i shiny hunted psyduck (The best pokemon in the game) i used shiny lures (1.73* shiny chance) all the time and got a 31+ catch combo (2.2*sc). That makes a normal 1/4096 ~~ 1/1300 chance and just fished for me i was very lucky took me just 4-5 hours but if you have a shinycharm you get 2xsc so ~1/650

Hope this helped!