I would rather say no than do it badly, so there is usually a wait.
I run Fracktal Works. This year I also took on a technical consulting role with Constellation Aerospace, a nanosatellite startup here in Bengaluru, which is roughly the shape of this work: somebody else's hard hardware problem, a few days a month. Advisory is the part of the week I protect for it, not a second business, which is why the numbers are small and the answer is sometimes no.
What I am useful for is the gap between a thing that works on your bench and a thing you can make two hundred of. That gap has eaten more hardware companies than any competitor ever has, and I have been across it a few times now.
What I am not useful for: fundraising theatre, deck polishing, or convincing a board that 3D printing will fix something it will not fix.