Reverb and tremolo should work without a footswitch. No RCA plugs required. The foot switch is for turning the effects off without having to turn knobs on the amp. That way, you can preset the effect, turn it off, play without, then turn it on when you need it.
I don't have a Sunn foot switch for my amps. I use a Peavey dual foot switch that came with my practice amp. It has a TRS (tip-ring-sleeve) ¼" plug, so I have to use a ¼" to stereo RCA adapter, but it works fine. I got my adapter at Radio Shack.