When is the best time to use your CoP 100% or 50% tickets?

You can use them at any time to help you get points in CoP but the ideal time is when there is a matching daily challenge event so that you can work towards getting points in both at the same time.

To really maximise your points the trick would be to check the daily challenges schedule and find 2 daily (hourly) challenges that both match the CoP requirements. For example on Friday there are 2 troop training challenges at 05 and 06 hours in the game time. If you start a tickets at around 05:45 you ill have 15 minutes to try to complete the 05 daily challenge or do what ever level you can and score points for both it and the CoP. Then at 6:05 the next daily will start and you have 10 minutes left on your ticket to score more points for the daily and also each towards the CoP.

There are opportunities like this on most days. If you have the time to spare then timing these events will help you get more rewards every day.