Yeah, make sure the rears are adjusted first.
You can pinch off the rubber hoses with some pinch off plyers and see what that does, if the pedal is high and firm remove them one at a time to find out where the problem is.
If it is still poor then it is either air or a bad MC. You can check the MC by removing lines and blocking off the ports with something. if the pedal gets high and firm it's not the MC.
I have seen calipers with bad orings that pull the piston back when you let off the pedal giving you a soft and low pedal. Also if the calipers have the bleeder on the side I have seen air get trapped in there. You can take the caliper off adn put a block of wood between the pads so you can tilt the bleeder up while bleeding