T-scan
The 'T-scan' is not really describing the scan, but rather the layout of the instruments ALT AI ASI
HSI
That is what is referred to as a T scan. The rest is really only ONE scan - that is the selective radial scan. This ONE scan changes (becomes selective) due to the priorities at the time. For example, if you are conducting a level, rate one turn, it will take you 2 mins to complete the orbit, so when we roll in (always on the AI) we don't need to scan the HSI for almost two minutes; (we will include it in our scan, but not AS A PRIORITY until almost on our heading). Nothing is going to change that we aren't expecting (we know it will take two mins to reach our heading). What we focus MORE on during this time is the ATT, our VSI and ALT and make ATT changes to correct any deviations in level or AoB.
This works for climbing/descending as well. If we are climbing for a long time, the ALT is not important until the later part of the climb, so we only scan it occasionally, until we are approaching the height, and then include it in our scan more often.
The trick (not really a trick at all) is to understand what is the important instrument (secondary to the AI that is) and scan it as and when required.
Remember, there is only one true scan, the SELECTIVE radial scan.
Good luck with your IF flying