That's the hard part. Tour stops have marshals at every hole. It could be easy to train volunteers how to run a clock. I think it could be easy enough to find people to do the timing and then simply allow the enforcement of penalties fall to the rules officials that are already there based on information passed on them by the hole marshals and volunteers working there. Maybe that works but maybe it doesn't.The added variables of golf make it much more challenging, but, I see what you're saying - then again, who is going to be clocking every group, from Thursday to Sunday?
No matter what the solution; players, the tour, and the volunteers/workers for each tournament need to be committed to making it work.