Unless there's more than one Gazeebo achievement then it worked for me. Sorry that my dumb luck paid off while your careful planning was much more convoluted.
Awaken the Gazebo
In Buried, Pack-a-Punch a weapon during round 1 with no one using the bank or Weapon Locker.
There must be another one right...
This achievement is really easy...did it on first attempt with big guy + chalk like the third day. Make sure you are busting barriers from max distance and chalk every gun and you'll do it with points to spare.
The easiest way I found to do this is as follows:
1) Gun kill all the zombies bar 1. (To keep the round going ofcourse)
2) Build the Trample Steam using the candy from the power room (running through the tunnels to get to the part and the candy)
3) Using the giant do the best pulls you can with him, you will need to open the bar but thats not to much.
4) after opening everything and putting all the chalks on (pay for the chirch, ghost house and bar. Use the trample to get into the court house)
5) AN-94 off the wall.
6) go through the house you will find that with 1 zombie left they spawn in a predictible manner allowing you to get past them with no issues, if you do have problems follow this path: enter and head to DT go back to the stairs and kill the 1 coming down at you, watch for the one at the top of the stairs around the right corner, then punch the bookcase if its not open yet and kill the witch behind, 1 more at the end of this tunnel then 1 more in the room and 1 more just before the exit.
7) go through the maze and pap.
I found this method works for me and I was able to repeat it with no trouble. Should take about 15 mins total to do maybe a little longer depending on your giant runs and if you miss any, I was able to miss one and still do this / have money left over after paping.