The two best means to get you a crawler are with the ray gun aimed at the knees, or the M1 w/ rocket nade at the feet.
The type 100 is a good weapon, you can find that teleporter area very tight to run around.
I truly believe it is best to move, but this is tough to do with a full 4 person team unless everyone has a light auto with easy ammo like the STG at the teleport straight from the main point. (or the Type 100) As that way everyone runs at near same pace, and your heavy machine gunner is not way behind.
Here is a good routine if you have a 'mobile' group that can keep up.
Once at level 14 or 15 time to stop 'camping' because you will be getting fewer reloads and should have made the effort to have at least one upgraded(pack-a-punch) weapon with a 'wall reload' available and at least one of the 'electronic weapon' or heavy machinegun.
Whatever area you are on the map, start the electric fence, then go to teleporter and as zombies start to make it through the fence, and your team is ready to reload, activate the teleporter and immediately run to the next nearest entrance OPPOSITE from the area you came from and turn on the electric fence at that entrance and head to the bridge. As zombies build up below you, jump (with ALL your team) and turn on the electric fence and head to teleporter. and REPEAT.
Made it to 31 couple nights ago with all players surviving until overun due to trying to revive a player that fell behind. I had not played with these folks before, but with communication and movement we made it that high. This is also a HUGE way to save a team should everyone else get knocked down.
IF you lose a player once at a high level, tell them to NOT worry about the box, just to get ANY weapon they can and upgrade it. STG is one of the better upgraded wall purchase weapons, or the FG. and then as you teleport back to main, quickly upgrade and then as heading back to bridge, QUICKLY get Juggernaut. Wait till the end of a round to get the Speed as that is centrally located and you can make it back to your team.