I take no credit forthis macro (but can't remember who made it), but I found it really useful for my alt mage:

/target <main>
/assist
/cast Skinning

And I also made this macro for fishing (if anyone is crazy/bored enough to try levelling that):

/cast [nochanneling] Fishing

You could make it equip your fishing pole too (if it's not already equipped), but I wrote that on the fly so didn't put it in. You still have to click both bobbers when you get a catch, but this macro lets you spam one button to fish on both toons, without interupting a cast if they catch at different times.
I found it quite easy (and more interesting) to fish with two toons as oppiosed to one, but I wouldn't want to try watching 5 bobbers. I might try this with a linked mouse but I'm not sure if that would be accurate enough.