If you are travelling in a bus, it is better to go through the theory and highlight important points. YOu can do it at the time of going to your office and coming back from office. You can utilise atleast one hour.
During lunch time, have lunch within 15 minutes and concentrate on studies for the rest of the interval.
If you are going on official duty to some other place, while travelling and whenever you have time, it is better to go through theory subject and highligh important points.
Alternatively, cultivate the habit of sleeping while travelling in a bus, so that you get recharged and can concentrate on your studies after reaching your destination (office or residence).
Best of luck.