depending on what collinite wax he has and what colour car, 476 and 845 are the lesser blingy of the collinite range and 915 being a little more glossy looking due to the higher carnauba content.
i wouldnt say AG Extra Gloss protection takes anything away but i wouldnt say it ads anything either, imo he's waisting his own time and product/money which ever way you want to look at it, collinite waxes are hybrid waxes ie they have carnauba in them and give a nice shiney finish but they also have sealant properties which is why they are so durable and generally dont need anything adding to them.
personally i dont and wouldnt touch AG products with a barge pole, if he wants an extra wet glossy finish thats better than egp then dodojuice is the way to go or swissvax,zymol if hes got a bottomless pit of money and no sense.
hope this helps
hmmm... swissvax and no sense? 
lol ok with the exception of mirage
,onyx,and a few others but anything over about £100 is waisted dosh imo, a guy on another forum posted up a detail on a newer shape focus rs which was matt black and he applied opaque to it and the results were very good.
