Although there are dozens of striders head for the base, there are only 3 striders will attack the building, you need to kill them quickly because they are moving quickly, remember to save after killing each striders.
This is the strider which will blow up the building walking style. faster than the normal strider. by the way after taking this photo. it blow up my saw mill. so you really need to kill it quickly. there is no time to take photo.

IF YOU DON'T LIKE TO READ. SKIP TO THE LAST CHAPTER.

there are bunch of hunter cover the striders. kill them all first. don't use Magnusson device before you kill all the hunters because they will shoot down it. If you are good at driving just use the car to knock them down. one full speed crash can easily kill a hunter. after killing all the hunters you can go handle the striders.

before reach the saw mill. park your car with one Magnusson device at the right of the saw mill. i'll explain later. the first strider and hunters come from the left. kill them and quick run to the car. the second strider come from the right. this strider would blow up the saw mill if you don't kill it fast. lucky your car has one Magnussin device on it. so run to your car. pick up Magnussin device, run to the strider, shoot it to the strider and blow it quickly. the second strider run pretty fast so it might be a little bit hard to target it. but before it fire the laser it won't move like two seconds. it the best time to shoot Magnussin device and kill it. and because it's speed the hunters are far away from it. you can kill strider first and leave the hunters there. remember to save.
i borrowed this map from white forest.
red line means striders which will destroy building.

3rd strider with 3 hunters come from the water tower. kill them. 4th strider with 2 hunters come from the crane. kill them. don't worry these two won't destroy the building. just kill it before them reach the base. but you better kill them fast because there are many strider left. you better make a save at here.

the 5th strider with 3 hunters come from the saw mill. kill them quickly. during you kill it you may hear the 6th strider come from the water tower. but seriously. don't care it now. because the 7th strider is coming from the crane and it will destroy the building on its way. when it spawn you need to head to that building immediately. there is a Magnussin device there in the building, quickly kill that strider with the same way you killed 2nd one. and don't forget the one come from the water tower. it won't blow up the building but it will destroy the rocket. and you need to kill it quickly, too. becaue the 8th strider is coming from the water tower too and it is the last one will destroy the building. kill them with speed and style if your friend is watching you. save at here even here is no more strider will destory the buildings.
IT IS THE MOST IMPORTANT PART. kill the 7th strider before 6th. remember the sequence and this will be easy. if you go find 6th before 7th you will see the strider destory building in front of you.

there are still many strider left. prepare for the last battle, you don't want to see them blow up the base after you save those building. so you must carry on.
these five striders take ramdon path, so the picture only show when and where they come from.

after defend the base you'll get the achievement.

why don't you just use the muscle car to kill everything you meet? it sounds like a plan.

There are M.device and a lot of supply in those houses. make the last wave much easier. I can defend the last wave without any strider reach the alarm area. or put a lot of sticky bombs on the last strider
strider : stop teasing me!