If you want a good Scorestreak you're gonna need to be going along with whatever the object is. Well this is a good way to try and maximize that with the streaks you choose.

To get Swarms more easily you should go for two "non-lethal" assist based streaks combined with a higher streak. For example on Swarm this might be Orbital VAST, EMP and the Swarm.

Get the Orbital VAST at 1,200 points, the EMP at 1,300 points and then survive. With all the points you get with the EMP you should then get the Swarm. Just stay alive!

Another combination could be exchanging the EMP for Dogs. Try it out!