1) Bring two pokemon, one w/Damp ability and a sleep inducing move, and one w/Trace abilityAnyone know to chain Galavanize Geodude?
2) Find the Geodude/Graveler to start your chain
3) Chain a bit (I'm not sure when the odds of a hidden ability 'mon appearing are best, I aim for above 30)
4) KO pokemon until only one remains
5) Put the remaining pokemon to sleep to prevent explosions for one turn
6) Switch to Trace user, learn ability
7) Switch back to Damp pokemon before the pokemon can wake up and explode
Damp Poliwag/whirl/wrath/toad with Hypnosis
Damp (HA) Paras/sect with Spore
Alakazam holding an Alakazite
Parasect and Porygon 2 are the best pairing I know of currently for SOS chaining Geodudes.
After Pokemon Bank is made available Damp Parasect that have been tutored the move Worry Seed in ORAS can be migrated up, allowing Parasect to suppress explosions, reliably put foes to sleep, and check for abilities all on it's own.