With Jamba, you can set it so the slave will select the same item as the master... or so that if there is a choice, then the slave does not mirror the master's selection.

I'm not sure if there is a slash command to loot, I know you can use /targetlastenemy to have your slave target the last thing you were attacking.
I use this in conjunction with /use skinning(master) to auto skin on a macro. Cannot get that to work for herbalism/mining, so my most frequently active main does those gathering skills, with a slave skinning everything.
If there is a slash command to loot, you could target last enemy and loot... but honestly, you'll probably have to right click on the enemies corpse with the slave to loot their stuff.