I have to do some shooting in a brightly lit manufacturing facility no windows. The light comes from fluos installed in a very high ceiling, and there won't be time to gel them.

If I white-bal the HPX-370, what's the best/worst I might expect for my footage. Would a filter on the lens help?

If your shooting with an HPX370 I don't forsee a problem. I shot under fluorescents many rimes with an HVX200 and was able to WB no problem.

Now, if you are bringing other lights in to shoot in that environment, it will be basically impossible to match them without gels if they aren't those new variable color LEDs.

I do have a Zylight Z90, but without a color temp meter, I'm not sure how I'd match it to the overheads. The owner of the biz (my subject) only leases the space, so I don't think there's a chance he'd know the make/mode of tube they're using.

If I could use the Z90, though, it would probably be a good way to eliminate some shadows falling from the lights above.

...what's the best/worst I might expect for my footage.

Flicker, or slow moving banding. This is due to the cheap magnetic ballasts driving the cheap fluorescents at mains frequency, and your camera settings not taking this into account.

Should be more or less easy to shoot without problems on this point. Shoot at a frame rate that's an even multiple of your local mains frequency, and a shutter speed that's an even multiple of local mains frequency, and you should be all right. For example, in NA, shoot at 30fps and 1/60th.

As to color, you're bound to see a more or less pronounced green spike from the cheap fluorescent tubes. You don't actually have to gel all the fluoros. You can also "gel" the camera lens (that is, use a good quality minus green optical filter made for this purpose). Then all you have to do is gel the lights you bring -- give them all a green spike to match the existing fluoros. The result -- cheap fluoros, green gelled cinema lights, and a minus-green filter on camera, will lessen the load on whoever is doing the color grading later. Of course, YMMV, so test, test, and test again.

If the space is as you describe and they are using HIBAY fluorescents they will not have magnetic blasts.

If the space is very brightly lit you should be able to use a sliver reflector for a bit of fill if needed and not have a mixed lighting issue.

WB won't be a problem. The colors may be a bit muted or wonky depending on the quality of the lamps they installed. You may want to shoot a bit of test footage for the client to see to make sure they are OK with the look.

Searched for "hibay" and couldn't quite tell what it refers to. Is it that the fixtures are mounted on a high ceiling? If so, that's what they are. the ceiling is very high and the space is very brightly lit by them.

If its a high ceiling and it is very bright in there then for sure it is NOT old school lights with mag ballasts. It will be a T5 or T8 fixture with electronic ballasts.

Sorry for the confusion. Try searching for HIGH BAY. That should work better.