In my experience as a SQ/DO and OG; you will be interviewed, selected and sent to OTS, followed fairly quickly (1-3 months) entry into UPT. Before the interview is a variable--in-unit vs off the street, passing a demanding physical (much more than a Class I), written exams (aptitude tests), the inrerviews at squadron and, often, wing level commander. If AR Reserve, the command also has a screening board after the unit has made a selection (more like a recommendation from the wing commander to the board). I went off the street, six weeks from approved to OTS, UPT 2 months after commissioning.
As you can see, lots of hurdles. If you want to serve and meet the physical standards, joining might help speed things up, as many units, especially ANG, prefer to select from in-unit people.
Once at UPT, unit equipment will decide which track you go down--T-1 or T-38. That's a year long school, plus conversion to unit type. Heavies typically take 3-5 months of additional training, fighters up to a year. It's like UPT all over in fighters. Back from all that, the unit will have a " seasoning" tour to gain experience.everyone of the pilots I sent thru in the 99-2005time frame are now at legacies, FDX or UPS. And have thousands of command hours due to the various wars and contingencies.
How much time at the unit depends greatly on the mission. As a LT, you won't have much for additional duties, but fly. In heavies, it's mostly fly, if the schedule has open trips/missions. Fighters fly, but kits of tactics and intelligence study.
GF