Stranger,
I can sympathize with you about the privacy issue that you will be facing in a few months. It’s a bitch. You’ll just have to find a way to work around it. Getting up extra early, going to bed extra late, or something! Just remember, necessity is the mother of creative adaptation!
As for the girth gains, the two best methods are clamping and pumping. Exactly what kind of PE have you been doing so far, and for how long? Whatever else you do, you should be jelqing. You can then add clamping or pumping or both. There are good beginners threads on both methods here. Read them and follow the advice. However, clamping is a more advanced exercise, so you should have a few weeks of jelqing under your belt to condition your unit before you attempt this.
As for speedy girth gains, there simply is no method. However, what you want are quick results. I discovered that even a small increase in girth made a noticeable difference and made me feel good about what I was doing. You should see some noticeable increase from the jelqing; you can perhaps include some manual squeezes. Then, if and when you give clamping or pumping a try, you will certainly see more noticeable difference. Just keep up a consistent routine, or this initial increase will be lost. It takes some time before any length or girth increase becomes “permanent.”