Make sure the resume fits the job. Definitely list any recent courses and actions you have been involved in. You do NOT have to have combat experience to get in with a PMC. Multiple years of combat arms is of course critical and even that can be absent with some good police experience like SWAT. Even non-combat experience in the box is helpful.
Send your resume to several and you should hear back from a few or at least one if you have the base experience they are looking for. Sometimes you need to take a lower tier security gig to build yourself up and make you appealing to the PMC. The PMC's will tell you exactly what they are looking for on their websites, these are not always written in stone! Some things are just mandatory, but sometimes execptions can be made in some areas with relative experince and such.
I would suggest you try 3C first just because they consider you an employee (and pay the employer portion of your medicare/social security) and they also offer 90 days on, 30 days off rotations! This leaves you out of the income tax exculusion though, but only being gone 3 months at a time and having 30 days at home with your family, 3 times a year is worth it in my opinion. From what I understand, the cost of 3C's train up is waived if you deploy with them. If you choose not to depoly after train up you get the $17K bill.
Blackwater generally has longer deployments than what 3C is currently offering, but you can get shorter terms with them also. Nothing is absolute. BW's train up cost more $20K and you will pay for it wether you deploy or not. They take it out in payments though and will offer you two years employment overseas. Due to the longer deployed time in the box, you can probably expect higher pay with BW vs 3C though. Other PSD guys that I have met on 90/30 rotationn were making about $145K due to the shorter work periods, but they also were not with 3C. Full time PSD's are pretty much starting about $180K. With BW though you are considered an "Independant Contractor" and thus you get stuck with teh self employment tax, yippee!
I'm am not The Authority on the subject but I hope my experience helped answer some questions. If you are serious in your interest, I can provide you some personal contacts in 3C and BW so you are not sending your CV in blind.