Halo wars co-op legendary

Hey folks. I’m looking to get some achievements and I figure getting the co-op ones and the legendary one are easiest to get when you’re getting them together. I seem to have some trouble with some of the levels on legendary on solo. For instance on Arcadia I try to make barracks and a few marines as soon as possible to garrison, but the ships explode before I get a chance to because the covenant keep bum rushing them. So if anyone wants to play co-op on legendary sometime let me know.