I rarely use global find and replace nowadays (just for complex regex replaces). I hold Ctrl-D until all occurrences are selected and type the replacement string (assuming occurrences are low in quantity, which they usually are in most cases).
Do you mean it's a lot of work to type in that prefix? Because vim automatically inserts it for you when you enter command mode while something is visually selected. A making a visual selection is very quick and easy.