Pretty basic and straightforward up until the end of the highway. If you want, you can grab rockets before first door on the highway. Get out of the tank and grab a hog before end. Run up to building headshot the two grunts to trigger the "Building Secure". Swap automag (or smg if you swapped mag for rocks) for plasma from grunts. There is an automag on the side of the gazebo nearest the highway, swap for rockets after you fire the first clip. Noob combo the brutes. (plasma overcharge + mag headshot). You have enough time to get back down to the dropship points after each wave, so chase down all the enemies that make it past you and head up, don't try to rely on Dare and Buck too much (they suck).
Reload rocks prior to second wave (alternatively use nades on the two drops and have rocks for last wave). Swap automag for carbine if you haven't already. Ignore enemies that make it past and focus on the hunter drop. Ideally you want two spike nades so you can just strafe left and stick the hunters in the back (oneshot kill if placed correctly).
Last wave is brutes and 1 chieftan. Use either rocks or nades on drop, overcharge the chieftan and spam headshots with carbine. Jetpack brutes like to scatter so it's not optimal to grab hammer. Best option is plasma + carbine. When you see the friendly phantom coming in, go to the pickup point.