Forty years ago if you wanted to measure equipotentials in the first year physics lab you filled a tray with saltwater, powered the electrodes with an induction coil, and located the equipotentials using the sound you heard in a hand held earphone. I soon discovered that one could use a DC bench power supply in place of the AC induction coil and measure potentials directly with a digital voltmeter. You could even measure electric field with a pair of probe wires attached to a voltmeter. Rotating the pair until you got a maximum reading gave you the field direction. I used this setup for a few years until the modern conducting paper experiment became available. It was less messy and no dangerous saltwater around power supplies. But a point charge experiment in two dimensions does not give a potential that varies as 1/r or an electric field that varies as one over r squared.
A 3 dimensional point charge experiment is possible using a large jar filled with saltwater. A metal screen is placed along the wall of the jar to serve as cathode connected to a battery or power supply. An insulated wire with just a tiny conducting wire tip exposed is hung in the center of the jar and connected to the DC supply as the anode (I.e., the point charge). Another similar insulated wire with an exposed tip is then connected to a voltmeter and used as a probe that you move around inside the water. I use stiff "bell wire." A pair can be used to measure electric field. Now one can get the 3 dimensional 1/r scaling of voltage as a function of distance from the point charge.