If you haven't seen it yet, the Cycling Tips rundown of mini pumps includes a section for Gravel/MTB:
https://cyclingtips.com/2019/08/the-...-mtb-mini-pump
The big takeaway for you might be that to inflate a tire took 20 pumps from a floor pump, 60 from a frame pump, and around 100 for the top performing mini pumps.