yes that is a bleeder cap across the final power supply cap. 470k. So that cap will bleed to zero. Will take about 20 minutes. If it was just that cap. The regulator fet would pull down the rest of the capacitors behind it. Probably to the point where the regulator runs out of headroom, then the leakage current of the regulator would take over, and it could take a couple of days to drain everything that way. The best way to add the resistors is to get a couple of ring lugs and solder the resistors to the ring lugs. Then after making sure the caps are discharged, unscrew the screws and put a resistor across each of the big caps.