I can tell you about the technique for an 0 200 Continental. I suppose other
engines would be similar.
Remove the spark plugs on the offending cylinder. Bring the piston to TDC and move it down an inch or so.Start feeding a 1/4" rope into the cyliinder. when you have filled the cavity slowly rotate the prop to compress the rope against the exhaust valve. Having removed the valve cover, use a spring compressor to remove the valve spring retainers. Reverse the rotation of the prop and remove the rope from the cylinder and to allow space for the valve.
Spritz the valve stem with penetrating oil and gently tap the valve with a soft hammer, eg brass. The valve will fall out into the cylinder. With a light directed into the bottom plug hole, capture the end of the valve stem and pull it out through the top plug hole. Remove the buildup on the stem with penetrating oil and a very fine crocus cloth.
Get an adjustable reamer and set it the slightest amount bigger than the id of the valve guide. Lubricate the reamer and run it down the guide, keeping it aligned with the bore. Inspect the guide to see if all the carbon has been removed. if so, run a paper towel down the guide to clean up the stuff from the ream job.
Try the valve in the guide, you do this by inserting a piece of safety wire with a semi circle bent on the end at a right angle into the valve guide..Insert a second safety wire with a semi circular loop on its end into the top plug. capture the valve stem near the head, as you do this ,capture the stem end of the valve with the other wire. carefully guide the valve stem back into the guide. If it moves smoothly, reinsert the rope into the cylinder and reinstall the valve springs and retainers. By the way, you need to hold the mini mag light in you mouth to illuminate the cylinder as you are capturing the valve for reinstallation.
After all of this, reaming guides is usually a temoprary fix. The primary reason that valves stick is because they are worn and combustion byproducts are driven into the guide. I believe also that Lycoming engines have a tendancy to bell mouth the guides, which again allows carbon to travel into the guide and causes sticking valves.