Allow yourself a set time for each body part and stick to it (no pun intended). Whenever waxers tell me that they take too long, it's because they don't have a system and because they don't work to a set time.
Being mobile doesn't help as you tend to leave too much time between clients. If you were in a salon you would have clients one after the other.
Remove all the hair from the one body part and only remove stray hairs. If you remove them as you go, it will slow you down. Tidy up at the end.
You're right to ask for help on this as you have to be quick and good when waxing.
Set yourself a test. Give yourself 20 mins to start for your next lower leg wax, including knees and feet. Do the front leg from under the knee down to the ankle, turn their leg to the side so you do most of the calf from the front, then the feet, then knees. Check and remove strays and apply oil so they're not sticky when they turn over. Then turn them over to do the final strip down the back of the calf. Apply oil to clean up.
Practise on mates and work to time. You'll get there. xx