I went from PPL- CPL/IR whilst serving. Made full use of SLC/ELC as mentioned above. Also took every opportunity to jump in sims or aircraft. Filled my logbook with every kind of flying I could get my hands on. I also, rather fortunately ahem, was sent on a tour where I was not particularly busy giving me plenty of time for the exams. In short, I managed every aspect of my training to coincide with my exit date.