Inflating airspring fork with Topeak products
A floor pump like Joe Blow has a massive piston, and the problem I can see is not about reading the pressure, but actually pumping such small amounts of air for this to be accurate (although the manometer may also not be too precise...). Technically you can use this, but as you mentioned it will not be accurate and there's not much you can do about it. 

You don't have to buy a specialist shock pump, however I'd recommend it. Hand pumps may be good enough, but you have to choose the right one, i.e. the one that can fit around the valve (there's often not much space around them), and that can stand high pressures, especially in case of rear shocks may be over 200psi (screw-on heads are preferable).

There are also three features that put a shock pump in advantage, based on my experience with a few:


They are thin and it's easy to pump up accurately even very small air chambers.
Most of these pumps have a button that allows to release small amounts of air if we pumped a bit too much.
This button also prevents air from leaking from the valve while unscrewing the pump head.