[Dragsinger]

Bob,

the pistons should easily move back in the bore. Opening the bleed screw is not necessary [although it is OK to do so] Simply removing the master cylinder lid/caps will allow the fluid to displace back into the master cylinder.

Suggestions;

a local parts store will have an assortment of tools designed to "push" the pistons, might even be able to borrow or rent the tool.

another common method, use a wide C clamp. With an old brake pad covering the pistons straddle the C clamp over the old pad and caliper housing.

Using a tool or C clamp, if the pistons does not easily retract you have a problem. Could be corrosion build up in the bore.