I'll give it a whack using words and maybe you'll get something from that.
Start by rotating the motor till #1 cylinder has its cam lobes pointing up--forming a "V" at the head/cam center line. You should be able to spin the tappet cups, as with the cam in this position, you will have measureable clearance. Measure the clearance of each lobe and write it down. Rotate the cups so the notches at the top of each are facing across the center line. you'll work from the exhaust side. The notches are there to help plink the disc out (the proper tool is a plier type affair with a grabbing point on each leg which straddle the cam. Insert the "J" tool between the two lobes with the open part of the "J" facing the intake side. With the tool resting its stepped sides of the "J" on the cup edges and the handle upright. Rotate the handle toward the exhaust side--it should push both cups down and lock itself in place allowing enough room to wiggle the shims out. Install both proper size shims and the rotate the "J" tool to release the cups. Check the new clearance. Rotate the engine to work on the next pair of valves (#3) -- then #4 then #2. -- Dave