Sha Lin is at heart a sniper. Eye him from a distance and try to come closer without him noticing. Then, jump at him with poppy bomb while firing sticky bombs. If you get the jump on him you will kill him.
A good Sha Lin knows how to avoid Grumpy Bombs, and you should never try to fight him alone. If necessary, stay closer to your teammates and use Poppy Bomb as an escape. Just try not to get hit by Impaler Arrow - and watch your back.