The principle is still valid. The local motorcycle repair shop was very busy and couldn't get to my motorcycle until very late in the day or maybe not at all. I said OK and walked to the nearby bakery. There I spent about $4 on pastries, returned to the shop and passed them out to all the working mechanics and their boss without saying a word except "for you." With plenty left over. The Yamaha was done in 20 minutes!
It is universal. When I needed hospital records for life insurance policies I would silently put a 2 pound box of chocolate on the nurse's desk and say nothing except "I really need these records today, but I know you are busy." Instead of having to wait for the copy clerk to make the records for me (usually in a week!), I would have them same day!