Remember every system a little different.Usually 2-6 months you see some kind of growth.
In my personal experience coralline grows the best under PC,VHO and T5's.Coralline grows slower under intense lighting such as MH's.Also your need some coralline already,so if none of your rocks has coralline pick up a piece or two that has it.Brushing the rock that has some may help to spread the spores around.Coralline started to grow the second month my tank was setup.Slowly its seems to be getting faster.I don't think growth peaks til 6+ months though.Remember coralline also grows slower than the nuisance algae so don't let them out compete it.
One more thing,I'm currently not dosing anything but I check to make sure my calcium,akalinity,and iodine are were they should be.My next test kit will be a magnesium,dunno if magnesium has anything to do with it,I want to keep it close to NSW as possible.
Best o Luck