Gah. You need to know the purpose of a decoction before you attempt to do it. You are removing mash, boiling it, then putting it back in to get to your next step temp. Aside from maybe holding your decoction at 168 for a few minutes, there is no reason to do anything other than bring it to a boil then put it back in the tun.
I just did a double last night on a hefe so I'll retrace my steps.
-Bring ~4gal water to ~138 degrees
-Add water to grain shooting for a step temp of 122-123
-Half hour later remove ~2.5 gal mash bring to boil slowly but steadily to avoid scorching
-Add decoction back to mash aiming for ~153 sacc step temp
-Half hour later remove ~2 gal mash bring to boil slowly but steadily to avoid scorching
-Add decoction back to mash aiming for ~168 mash out temp
A triple decoction would add an acidification rest so your initial dough in temp would be ~105 then you would do a decoction to get to your 122-123.
I do triples for pilsners and doubles for hefes (though last night was my first hefe brew), and a single decoction on every batch to mash out. I aim for about 45 minutes per rest (including the time the remaining mash sits in the tun while the decoction is being boiled). Like I mentioned some people advocate letting your decoction rest at 168 to terminate enzyme reaction but I don't. Also, for light beers you don't want to boil your decoction too long. For something like a dunkelweizen you could lengthen your rests to an hour each and do a good hearty 10-15 minute boil on each decoction.
Once you get a feel for decoctions, they are really fun to do, and eventually really easy too. You do add some time on to your brew day but what's so bad about that? I say nothing.