I've always fitted the piston to the rod first - to avoid struggling with the circlip in the confined space under the cylinder.
I then use a home-made ring compressor which is basically a strip of shim (wide enough to cover all the rings) and a large jubilee clip - loosen the clip enough so it'll slide on the piston and then gently tap the cylinder down onto the piston using the flat of my hand. Being thin it'll then easily pull out from under the cylinder.
Done it many times on different bikes and never a problem.
