I don’t have a lot of tools. A couple screwdrivers, wrench/rachet set, couple hammers. Basic stuff.
How To Compress Brake Caliper
Brake Caliper Compressor
you can use a small piece of wood wedged between the piston and caliper then pull back and forth
until the piston slides back.
on the other hand, a c or g clamp is fairly cheap to buy in a hardware or diy shop
Try loading your new pads on the calipers without compressing them and putting them back on over the rotors, let us know how that works out for you. live and learn I always say.
leave your old pads in and pry them apart with a couple screwdrivers, once the caliper is compressed install the new pads, takes a bit of hand strength but I do it all the time, and I actually have all the correct tools. crazy huh?
some times you can push them in with a srewdriver but it’s so much easyer wiyh a c-clamp
Hope this helps!