Replacing pads and no bleeding the system.
I have done this on my RV6A and it works...
Plug off the brake line as soon as you disconnect it. Plugs and caps can be found at Aircraft Spruce. You can also use brass fittings from hardware store. You are only going to install finger tight 45 to 37 deg. no problem.
Before you press the piston (with the new "O" ring) back into the caliper, pour some brake fluid into the cylinder about 1/2 full. With the fitting capped (on the caliper) press in the piston, head first. Once the O ring is seated in the cylinder, turn the cylinder with the piston skirt down on the bench. Loosen the cap and gently push down on the caliper. Have a cup under to catch the expelled fluid. When the piston is flush with the caliper surface, and fluid was pushed out, there is no air in the caliper so tighten the cap by hand.
Install the caliper on the wheel with the pad plate. At this point, make sure your brake fluid reservoir is 80% full. Remove the cap from the caliper. As you remove the cap from the brake line, it is going to start leaking... as it is leaking, air will not get in..... connect it to the caliper and tighten.
Complete the brake install. Check fluid level. Gently press the brake pedal for that wheel till it stops, to seat the pads. Release and press again. If brakes are firm, YOU ARE DONE. If they are spongy, then proceed with bleeding procedure. I have had very good luck with this procedure.