I will chime in and say that most of my accounts, I do not install bedding plants between established shrubs much. Often these plants is separate from the established landscapes and is so by the use of edgings. The reason is the mulching depth. I would not place any more than 1/2 inch around bedding anyway.......causes excessive moisture retention and often stem disease. Established shrubbery, I will place anywhere from 1/2 inch to 3 inches. Depends if the landscape is new.
To answer your question, you will probably benefit from wheel barrow, casting by hand, and by dumping and smearing.