Griznah and I figured this little tidbit out today, I'm sure someone else has but I haven't seen posts about it anywhere when doing the research.

This will be the fastest way you can do this at this point, without an addon, and it wont require to much work either!

2.4.3 Introduced a new script api for wow: GrantLevel()
*note: your target needs to be in line of sight for this to work.

Code:
/script GrantLevel("MyCharacterName", 1);
or alternatively

Code:
/script GrantLevel("target", 1);

Unfortunately, with our testing, we found that changing the level had no effect on the process, it only grants 1 level.

Now, great, we can pop up a window on our veteran account and grant a level pretty efficiently - Oh wait, now we have a pesky dialog on our Grantees screen, I don't want to push my left mouse button 59 times just to ding 60, that's crazy...and if you don't want to either, just use this snippet to click "Accept" on that dialog.
*note: this button may also accept other things, that you may or may not want to accept, it's a very generic name.

Code:
/click StaticPopup1Button1
So it's pretty simple, just throw these buttons on the same button and press it 60 times. I think these macros would fit in nicely with MultiboxerV2 *nudge*

Oh and the summon macro, this one is simple but I thought it was neat so here it is:
Code:
SummonFriend("MyCharacterName")
I haven't used this method personally yet, but I will be this weekend - Let's see who can level to 60 in the fastest amount of time now...

Hope you guys find this information helpful!

Who can go faster than this?
Current Record: 51m 28s [Griznah]