It really IS a good deal. I highly recommend it, but be sure you are going in for the right reasons. Don't try to use it as a stepping stone.
OK, since I've "been there, done that" I'll step up and give you the rundown:
Most Air Guard units will get 1 SUPT slot per year. Some may get more, and I know some don't get any at all. You'll be competing against guys already enlisted in the unit, but it's not unheard of for them to pick an outsider. In my case, I was enlisted there, so they knew me. I worked full-time there in my job as a civilian "Technician" also, as I was putting myself through college and needed serious bucks to do that as well as pay for my ratings needed to graduate. Those jobs pay well, and I was lucky to get one. If you want to enlist in your home unit or your "dream unit", it will involve picking your job (YES, one benefit of the Guard over AD AF) signing up, going to boot camp in San Antonio, then to Tech School to learn your job, then back home. I did it all in one summer between semesters. If you have college credits or a degree, they will promote you to E-3 or so after basic training, which helps alot money-wise while you're in Tech School. For those who have not yet finished their degrees, most states give 50-100% tuition assistance when you get back, plus the VA will pay you additionally just because you are going to college. It's a good deal, and I could not have done it all myself (no loans either) if it hadn't been for the Guard. I'm not bragging or anything, I'm just trying to give you the straight scoop on what is possible if you need it (like I did).
OK, they have interview boards once a year usually, and to apply you need to have taken your AFOQT. There may be other requirements now, so check. In my case, after the interview they narrowed the field down to 5 guys, then sent all 5 to take the BAT test. Then they made their decision. Some units may work it other ways. One unit I interviewed with (not my home unit) had so many guys show up for the interview that they decided on the spot to give us all physicals right there, hoping to narrow the field that way. It was funny for us, not them, when ALL 25 or so of us passed their quick flight physical and they had to interview all of us. I think they invited many people in for an interview, thinking that some/most would not show up. In the interview, they are really trying to decide if you have what it takes to make it through SUPT and follow-on training, and also are seeing if you will fit into the unit. It's a big deal because they know they will be stuck with you for the rest of your career, and will have to go to war with you if they are ever called upon for that. There is no way to game this part, so just be yourself. You probably won't be asked any technical questions, but will be asked situational and background questions etc. At one interview (again, I was desperate and this was not at my home unit) they asked me what kind of beer I liked. They are trying to bring you into their family. Personal references count heavily, especially from people inside the unit.
So you get selected. They will give you a Flight Physical, send you to Flight Screening (or at least they did then) for 1-2 months, and then to the Academy of Military Science for 6 weeks (may be longer now?) to get your commission. Then you will go to SUPT (one year), survival school (Land and Water), then fighter lead-in (if applicable, and 2-3 mos I think) then to your schoolhouse for the unit airplane (6 mos to a year maybe). Then, you come home to your unit and get qualified locally as well.
It's really about a 2-3 year deal right there, from interview to back home flying the airplane. Don't give up if they don't hire you at your first interview. They may like you, but they may have others who may be running into age issues etc that they need to select "now or never". It took me 3 years of applying, and by then I was running into an age problem too. It was 26 1/2 back then to start UPT.
Anyway, I think your odds are better if you enlist in the unit you wish to apply to. It shows commitment and has benefits too. If you are sincere, it also gives you a chance to bust your a$$ and show them what type of person you are. Even if you don't get selected for a pilot slot, you will make some friends for life while there and have some great times with them.
That's it in a nutshell. Some others may have some different info, but this should still be fairly accurate. Good luck! PM me if you have specific questions.