Components for adjusting the current and voltage of a very high energy power supply
You could buy a VARIAC. This is a variable transformer. Such a device takes in AC mains and can output anything from 0 to 110% of the incoming mains voltage. The devices that I have seen have an internal toroidal single layer winding in a ring core and have a dial that moves a brush along the winding. Check the rating of your MOT pair and rate the variac accordingly. Confirm your mains voltage and mains frequency and specify the variac. These devices are simple, robust, easy to use and quite heavy.