This is indeed where the skills come in, you need to know why you are detting... Too lean, too advanced, ACT's too high, etc..
Easiest way to cure it is to pull the timing back a few degree's, if your fuelling is around 11.9:1 then you are not lean, and if your ACT's are under say 50degree's (although apparently up to 60deg is not uncommon) they are ok, so probably just too advanced.
If you are lean or have high ACT's then retard the timing to stop Det immediately, and cure the problem (more fuel, bigger IC, lower boost, whatever is needed) before attempting to advance the timing again.
IMO if everything is good and you've pulled the timing back to 10deg BTDC and your still getting det then drop the boost a fraction as you have probably reached the limit of your spec.
To give you some idea my peek VE (4800rpm 27psi) advance is 16deg BTDC progressing to 18deg at 7000rpm, this will of course vary depending on your CR, Turbo, Cam, headwork etc.. so it's just to give you an idea really.

This is all of course just my opinion from my limited experience!!