No, this is not an another Nitro Boost + parachute repost. I used to do this all the time on my engineer warlock toon back in the day.
Anyways, what you will be using is:
World Enlarger
Baby Spice (Obtained from Dalaran cooking Daily)
Small Feast (if you want)
No longer stacks with Noggenfogger elixirs though:
"Cooldown removed from Noggenfogger Elixirs. The shrink effect will no longer stack with other shrink effects."
Simply use all these items before you grab the flag (note: If you attack someone or get attacked before doing so the shrinking buff will be removed)
You will be extremely hard to see even close up, if i remember roughly 20 yards away, you are basically invisible. Also, unless the enemies uses Tab to find you, you are untargetable, especially if a partner is with you (they will select him with tab). Have fun!
(I've also been told it makes your aggro range in PvE smaller as well, not certain about this though.)