How much voltage do you need to force charge into a material? If I'm using electricity not to induce steady-state current, but instead to force as much charge as possible into a given material, given I know the relevant properties of the material, how do I calculate how much voltage and/or time I need to put a given charge on the material?
Assume that the circuit is open, in that I'm taking one end of a battery or otherwise some circuit that doesn't terminate on ground, and feeding it directly to the material, with the goal not of sustaining steady-state current, but simply pumping as much charge as I can into the material before current stops flowing. This design could also be thought of as a capacitor without an opposing plate, with an air (or equivalent) dielectric.
A quick glance at the equations for a capacitor show that without a second plate, an infinite amount of voltage is needed to put any charge on the material, which is easily disproven by touching a doorknob after rubbing socks along a carpet, so those aren't the equations I'm looking for.
What equations can be used to model this situation?
 A: You charge an insulator (e.g.  methyl methacrylate a.k.a. Plexiglas) by targeting it with a cathode ray.  The abstract linked below quotes a value of 2 million volts.
I remember this sort of thing was done in the ion implantation lab where I worked as a student years ago.  Those voltages were lower, probably no more than half a million volts.
https://www.researchgate.net/publication/226904728_Electron-beam_charging_of_polymethyl_methacrylate
A: 
how do I calculate how much voltage and/or time I need to put a given charge on the material?

If the material is not conductive, then it is difficult to put the charge across the material.  Since charging up one tiny point doesn't really affect the rest of the material.  So "how you do it" would be critically important to understand how long it would take.
Single-ended items also have capacitance, but the amount is far below that of something like a parallel-plate one, so they're not used in circuits.  But they still exist and you can (for very simple geometries), calculate the capacitance.  Then you can use the standard equation and find the tiny amounts of charge that can be moved this way.
Does there exist a single plate capacitor(conductor)?
Capacity of an isolated spherical conductor
https://physics.nfshost.com/textbook/09-Capacitance/01-Definition.php#:~:text=For%20sphere%20A%2C%20CA,10C2%2FNm.
The time it would take would also depend on the inductance, which would also be unlikely to be modeled.  Safe to say that for most materials in most situations, the time constant will be minuscule and the charge time will be nearly instantaneous.
But static charge buildup on objects doesn't happen in this manner.

A quick glance at the equations for a capacitor show that without a second plate, an infinite amount of voltage is needed to put any charge on the material, which is easily disproven by touching a doorknob after rubbing socks along a carpet, so those aren't the equations I'm looking for.

Not infinite, just very high.  Turning it around you could say that with this quite low capacitance, even tiny amounts of charge are sufficient to create very large voltages (hence sparks).
