I roll the rear tire under bike, slip caliper onto rotor, slide bolt in partway so it stays in place, standing over bike just above tire, lift rim/tire, push/wiggle axle so it catches, use foot to lift/assist hand to position wheel while pushing axle. Usually works for me. Make sure caliper is slotted in the proper position. Met a guy that rode from Chicago to Nevada and never realized the caliper was not slotted properly on his Vstrom. He realized this the first time he backed his bike down a hill at his campsite and the caliper just about fell off, only the hose was holding it on at this point.
I was in the next campsite when I saw him do it.