If you want to bot, you could bot alching at SW under the big pile, or you could try to find a good stun alch bot and set it up somewhere where you won't encounter too many people.
If your doing it legit, bursting/barraging rock lobs is a great idea because you get greap exp and you collect the charms you will need to get your summoning up. However, if time is a factor (because rock lobs take awhile to setup) I would go to ape atol and burst/barrage there for maximum magic and HP experience. That is where I got 99 magic on 2 accounts legitimately