Just for everyone who'd like a more detailed solution about the boosting methods and the skills needed for this, I thought i'd make one.
It takes 951,000 skill points to get all the skills you need for this achievement.
Skill List Firepower Lv.1 12,000
Lv.2 29,000
Lv.3 75,000
MeleeLv.1 10,000
Lv.2 25,000
Lv.3 75,000
DefenseLv.1 3,200
Lv.2 28,000
Lv.3 80,000
Lock-On Lv.1 2,800
Lv.2 31,000
Rock SteadyLv.1 3,500
Lv.2 33,000
Critical Hit Lv.1 7,500
Lv.2 13,000
Lv.3 32,000
Piercing HitLv.1 12,000
Lv.2 28,000
Lv.3 55,000
J'avo KillerLv.1 3,000
Lv.2 27,000
Zombie Killer Lv.1 3,000
Lv.2 28,000
Combat Gauge BoostLv.1 70,000
Lv.2 90,000
RecoveryLv.1 10,000
Lv.2 70,000
Field MedicLv.1 12,000
Lv.2 95,000
Boosting MethodsThere will be a video below that was made by zerolimitz12/Ahkamon over at x360a and as far as I know he is the one who found the method for Chris's Chapter 5 20k run, it'll show how to do it in about 7 mins with a partner and it'll take 9 minutes give or take by yourself. Here's the link to his thread explaining it into further detail and the video can also be found there as well,
http://www.xbox360achievements.org/forum/showthread.php?p=53...Another method that i've heard of is playing Leon's Chapter 2 and just rushing up to the Cathedral, where you would just kill all the Shriekers and Bloodshots and pick up all their Chess Pieces in front until everyone is dead and go inside and once it saves as you enter, just quit out and repeat. This one is not consistent though, some people have said that you can get about 100k in 30mins and some have reported just around 30k in that time.
Of course you could always do Mercanaries, it's much more fun and with a good partner you could blast through everything and rack up the skill points in no time, "Ebonhawk01" had a good solution for post-campaigns for the Mining Beast map.
Feel free to ask any questions and if you're going to leave a negative vote please explain why, you're not helping the cause by not telling me what I did wrong.