Curtain rails and blinds: the first ten minutes is all measuring
Ceiling-fix into a suspended gypsum ceiling is the classic trap. Screws into the board alone will hold for a few weeks of gentle use and then let go, usually at 6am when someone yanks the blackout open. The correct approaches are either longer fixings that pass through the void into the concrete slab above, or rated hollow-ceiling anchors with the load spread across extra brackets. Ask your technician which one they are using; the answer tells you a lot.
Time budget: a straightforward single rail or roller blind is 30-45 minutes per window; a ceiling-fixed double track with careful levelling runs closer to an hour. The finished check is simple: the rail is dead level (water finds crooked rails instantly, your eye takes a day), gliders run end to end without catching, and the brackets do not flex when you draw the curtain briskly.