Stress the importance of complete understanding. Express confidence but avoid cockiness. Be alert to signals from your audience. Yes-Yes in your eyes. People often send these unspoken messages through the eyes, the expression, the hands or the feet.
Actions speak louder than words.
Any manager will, on occasion, have to convey what the employee will view as bad news. In this case, don't pass the buck, stall or avoid the issue. Respond firmly and directly. Management has the role of making decisions then accepting the responsibility for them. You can disapprove of the job or product but still approve of the person.