Metal buildings ... both a blessing and a curse.
"Minor" pipe runs can be done using beam clamps and Mineralacs. You'll still need to mind your bends, as the saddles around the uprights and doors add up.
Going vertical -if you're strict about it- means you first need to build a secondary support, as the Z-purlins are usually more than 10ft. apart.
You WILL need some horizontal runs across the ceiling. Again, the structural steel is far more than 10ft. apart; 25ft. is common. So .... cut to the chase ... you WILL need to construct a proper trapeze and hang it from the Z-purlins up there. Since 'extra' pipes keep appearing, design it plenty big.
Where you do need to mount to the sheet metal 'skin,' your best bet is the old-fashioned toggle screw.
As a 'design note,' plan on having a junction box at every column; sooner or later someone will need something there.
While it's a pipe-bending nightmare, try to place your receptacles between the flanges of the I-beams. That's the only way to protect them from forklifts, etc.
