Slum It in the Summit

If you're having trouble completing The Yak Wash part of the achievement, you can find more quests by killing one of the Burilgi yuangol. Once you kill one, Yakity Yak pops up. As well, they drop a quest starter item: Muskpaw's Keepsake.
Happy yak washing!

Kun-lai Side Story Quest Tree From Whiterock

   S)Temple of the White Tiger{H}(Multiple zones)
   +)A Celestial Experience   {H}
   a)A Witness to History     {H}
   /                           |
The Shrine of Seven Stars(A)* The Shrine of Two Moons(H)*

The Ordo Warbringer{A2,H1,H2}*   +)The Kun-Lai Kicker([zone=6426])
 |
S)Muskpaw Ranch{H}
+)The Missing Muskpaw            +)Fresh Needle Scent
 |           \
b)Yakity Yak b)At the Yak Wash   +)The Late Mrs. Muskpaw
 |           /                   b)The Fearmaster
c)Back in Yak

The Ordo Warbringer{A2,H1,H2}* Barrels of Fun{H}* Pandaren Prisoners{H}*
                          \          |            /
                          S)The Missing Merchant{H}
         +)Repossession   +)My Son...
                          d)Father and Child Reunion

+)The Waterspeaker's Staff +)Enraged Vengeance +)Free the Dissenters
                         \  |       ┌───────────┘
                         d)The Ritual
                         e)Cleansing the Mere
                         e)The Fall of Shai Hu

Legend:
S means Skippable
+ means Can start anytime, prequests not needed.
(A)/(H) means Alliance/Horde only.
{H} means Quest Have Horde Variant, click {H} for it.
* means another Quest Tree.

I was having a terrible time finishing this Achievement because I was missing The Thunder King and Zouchin Village. It is because I was missing the quest One Traveler's Misfortune. Once I started that is led me directly to the last two, and bam got Slum It in the Summit within 15 minutes!

Hope this helps!