In a typical fender circuit, there are three capacitors in the phase shift network. The deluxe reverb circuit shows a .022uf (connected to the plate of V5A), then a .01, followed by another .01uf. By increasing the value of one or more of these caps, the oscillator frequency can be slowed down. Try doubling the size of the .022 cap, by simply paralleling another one across it. Tack solder, and check the results. Not slow enough? Add capacitance to the .01's. In some instances, the old caps may have drifted down in capacitance. Complete changeout using film types may be a wise investment.

Usually, I find that replacing one of the .01 caps with a .022 slows the tremelo down sufficiently. In situations where I decide to replace all three caps, the small metallized polyester caps (such as the blue Xicons) fit easily between those four eyelets. 

 I would like to add.. some fenders have a weak trem. and some models use a 100ohm resistor and some use a 47ohm resistor ..changing to the 47 ohm gives it more..intensity.. {~}==:::