The 'know a guy' aspect is really just a jump on navigating the hiring process - DIA is big enough it's hard to cut corners for less than an SES. So, you've still got a solid shot without any direct connections.
It sounds like from your post you're interested in a HUMINT collector position. From my experience only CIA and DIA (outside the DoD) will take on HUMINT collectors on a 'will train' basis. DIA, at least several years ago, really like to hire young folks and send them through several years of school - about a 3-5 year pipeline to full collector but they got a lot of exposure to the analytic (main) elements of the organization. However, back then the FTC graduation rate was not the best and since then everyone is required to go through FTC. So, they may be more inclined to take on more experienced folks. The option of starting in another specialty and moving over is always a good way to go though. Like a lot of difficult schools there are always last minute drops so somebody waiting in the wings to go can do pretty well from DIA and some DoD units.
All the other source collector positions I know who have civilians generally are going to take folks with all, or almost all, of their collector training completed. Not sure if you went through any levels of ASOT when you were in SF but that might open some doors with those other places.
If you're in the RC, or are still eligible for the RC, you might consider joining one of the RC units that drills with DIA - 3100, 3200, and 3300 SIG. They're replete with folks double-dipping (both IC civilians/contractors and TPU RC Soldiers). That's another great way to get a foot in the door.
Feel free to PM me or
@Marauder06 if you'd like to talk more. Not to share his business too much but
@Marauder06 graduated from a very prestigious school run out of the DIA.