SM
Try turning side on to the FOP keeping the touchline to your right and the flag in that hand (running right wings) and learning to run backwards (There is a good FA training diagram set for setting out some cones and practising this, running then turning or changing direction, your RDO or CFA instructors should have a copy) I used to practice with radio 5-Live in my earpiece as I ran up and down a deserted but well lit bit of park with a flag, starting, stopping, turning, changing hands and signalling to the live commentary - a few locals called me 'that nutty referee' - they're right, I had voices in my head!
20-25 minutes live virtual top class footy + warm up/down is a bit beyond my fitness now, but doing it that way back then I found the time flew past improving my stamina and technique at the same time. Facing 'backwards' you need only then rock your head or glance through 90 degrees, giving you a view of both touchline and 2nd last defender(s) but also everything going on in between.
When you need to stop to signal either way, you can smoothly change hands below waist height as you turn on your heel to face the FOP, looks really spot on if it's done right, just takes practice. With good eye contact and the flag clearly held away pointing to the ground a foot or so in your left or right hand for a split second if you change hands can lead your colleague very clearly if he's looking to get out of jail, again it's just practice, but it prevents flagging to quickly or against your colleague in the middle.
The good tip about stepping back a yard or so from touch can be helpful in more ways than one, so long as half a dozen subs aren't warming up alongside you, you might need to find better ground at this time of year with the touch lines (our patrol path) being in such bad condition underfoot and run your line a step or two back,I always go out of my way during pre-match walkabout to have a good look at where I'm working, just to check I'll be safely running and not having to watch where I'm stepping.
Best of luck to you mate, do it bit by bit, 'evolution not revolution'