If you have access to a variable voltage power supply, (I use a Heathkit IP-17, goes up to 400VDC, 100 mA). I use a 10K 10 wat resistor in series with the plus side, connect the electrolytic and set the PS to about 80% of the voltage rating on the cap, and observe the current. This will slowly re-form the cap, and it can be checked / tested by measuring across teh cap, and measuring across the 10K resistor will give an indication of any leakage current that may be present.
If you don't have the variable power supply, a simple set up can be made with a 300VAC output transformer, a rectifier diode (1N4007 is good enough) and a cheap variac in order to control the voltage and bring it up slowly.
If you don't haev a variac, then wire in a ceramic light socket in series with the primary, the bulb will act as a current limiter, start with a low wattage bulb, 25W or less, then sstep up through 40W, 60W, 75W, etc as required. FOr lower current limiting, use a "candelabra" type socket and the smaller 7W "christmas tree light" bulbs can be used to start out with. If the bulb satays bright, and doesn't dim down then the cap is bad (shorted or very leaky). THis is pretty much "Fred Flinstone" technology, but it works... Just search for "chicken stick" on this site, I'm sure I've written this up in more detail Yellow_Light_Colorz_PDT_02
Here, I'll save you the trouble....
Years ago, I made up a simple but vital piece of test equipment, forever to be known as the "chicken stick". Basically a 6 foot long 2X4 piece of wood, with an outlet box on one end, and a regular wall switch box on the other, and a ceramic light bulb socket next to, and wired in series with the outlet box, and, of course, a line cord. The device under test was plugged on, a lightbulb (or a properly rated screw base fuse) was inserted into the lamp socket, and then, the device io be tested (or sometimes detonated) was turned on with the switch on the far (safe) end of the stick. This ensured an extra margin of safety, by having to be at least six feet away when the switch was flipped.
(Yes, I had one too many catastrophic capacitor explosions in my past).
Actually I remember seeing a similar arrangement on a test and repair bench when I was doing techie work in the army way back long ago (1969-1972). Sometimes the term "fire it up" was just a bit too literal...
Later on (1993-1996) when I was doing product safety testing, which involved intentionally creating malfunctions in power supplies, and making sure that they failed in a safe manner (no flames, gushing hot fluids or shock hazard) , this same technique was used, as sometimes the test resulted in a rather spectacular explosion, showers of sparks and hot electrolytes, and shooting flames.
/ed B in NH