This tool works very well as long as you do not try to use it to depress the valve shim buckets by rotating the tool between the camshaft and buckets. There are some YouTube videos showing that method and it only works if your valve springs are made of spaghetti. Rotate the crankshaft with a wrench to turn the camshaft so that the cam lobes depress the shims/buckets. Then insert the tool and try to keep it as centered between the two adjoining buckets as possible. Finally, rotate the cam lobes off the shims and the tool keeps the buckets depressed. If not careful in positioning the tool in the center, it may only hold one bucket down. No biggie, just use the cam lobes again to depress the buckets so the tool can be repositioned to hold both buckets. Remember to make sure that intake and exhaust valves on the same cylinder are not open/depressed at the same time (I.e. Intake by cam lobes while exh open by tool holding buckets down). Also, absolutely DO NOT remove the tool without shims in the buckets!
The tool seems to have gotten better with use, but I started storing it in synthetic engine oil. The oil allows it to easily glide around the camshaft and push down on the valve shim buckets. A quick wipe prior to use and it is ready to go.