I can't offer much; if I was working on it, I would first have blown out all the lines with compressed air and filled things with water (brake fluid is made from alcohol and glycerine - glycerine is derived from animal fat) - when brake fluid absorbs sufficient water, the water reacts with the glycerine and over time it reverts back to near it's original composition and the resultant residue resembles jelly, tapioca or sand depending on the state of decomposition. Water softens the residue and makes it easier to blow out. I would then rebuild the calipers and the master cylinder (NOTE: any master cylinder in good working condition will make the brakes work). I first bench bleed the MC and tie the lever back to prevent fluid from running out and air getting in. I then fill the rebuilt caliper with fluid and install the piston just enough to purge the air from the caliper. I install the line onto the caliper. I do this for all the calipers on the vehicle and place a c-clamp on the caliper to lock the piston in place. At this point (with all the lines connected) I remove the tie holding the lever on the MC and starting with the caliper farthest from the MC and use the c-clamp to press the piston into the caliper body while holding the line fitting at the apex - this pushes fluid and air back to the MC. When the pistons are all depressed and locked in place with the c-clamps. I pressurize the system with the master cylinder lever and while holding pressure on the system, crack each line fitting to purge any air trapped at the fittings. You will not hurt the c-clamps by leaving them on the calipers and operating the brake - in fact they will act as a spring flexing with pressure and forcing fluid back to the MC further purging residual air trapped in the system. It is beneficial to do this with the handlebars turned as far to the right as possible placing the MC at it's highest point.
You can use DOT 3, 4 or 5.1 and mix them if necessary. The only difference in those DOT grades is the boiling point. Higher grades have higher boiling points. DO NOT USE DOT 5 - IT IS SILICONE BASED AND ONLY USED IS SYSTEMS DESIGNED FOR DOT 5 !
