JK starter, pop up, HP, JK, torpedo. I don't know how much damage that does. I have not played in months. I guess you can buffer in more hits in the corner? I don't know.
After a bunch of tries I can usually get the infinite going. My standard Raiden combo is:
JPS, 4 hit pop up, teleport, aaHPHP, aaHP, teleport, reverse aaHP, aaHP, JK, Superman for 61%, I'm not sure how much easier the actual inf is on N64, but that combo is doable on PSX.