Disguise/Soundless armor usually takes care of it and the Decrease Agi but it's not 100% effective, but good enough.
If you'd rather switch with GTB, make sure that you don't do any skills while it is equipped because the skill's SP consumption is doubled, also make sure that you switch back to Tirfing (my recommended card) Guard/Buckler when you're killing your mob.
Edit: I think you're better off carrying a bit of GJ (and using the Disguise Armor). You don't need much for an hour run anyways. o.o