That is certainly not the correct way of doing things. Prune, clean up with blowers and rakes and then turn over the mulch a little and it will be good.
I have never ever been a fan of charging by the hour on anything. To me when you do that its like your telling the customer your are not 100% confident in your knowledge and abilities to complete the job. Review the job, determine your hourly rate accurately, and then determine how long it should take and give a price. IF you under estimate well thats unfortunate, but its part of business and you learn from it.