firstly flush out all old brake fluid, its a very easy job buy about 1 litre of DOT 4 brake fluid - make sure its genuine stuff.
Find an old jam bottle, find some clear plastic tubing that fits very hard over the bleed nipple, place the old jam bottle in such a way that the entire contraption sits ABOVE the bleeder screw.
do it as
RL
RR
FL
FR
Suck out all old brake fluid from the bottle in the engine room, wipe clean any muddy stuff in there and then final wipe with clean brake fluid. FIll till the top with new fluid open the bleeder screw - now get in the car and very slowly pump the pedal only half stroke at max - repeat and check.
Keep view of color in the pipe - when the color changes to the new fluid color the wheel is flushed repeat the exact same for each wheel. You will use about 700 ml to 1000 ml of brake fluid for a proper clean flush.
DO NOT LET THE PEDAL PUSH TO THE FLOOR, If you do so you WILL DAMAGE the internal seals in it. If your pedal is already there then its best to rebuild the master cylinder first then do this procedure.
The ABS sensors can be checked while in place. Dont recall their resistance at this time.