You can always practice cutting wedges with random pieces of scions you have laying around. I used to be absolutely horrible at cutting wedges but I got better with practice. That tool looks like it may be what you need but the length of the cut is small so the cuts the tool makes on scions will only be useful for cleft grafts. The angle of the cut will be too wide for bark grafts, side clefts and veneers.
If you will be grafting more in the future, grafting by hand and blade is a great skill to have. There have been many situations where I had to adapt on the fly because the scion was too short, too thin, too thick, there was a node, I messed up the original cut and a numerous many examples where a grafting tool would not have enabled me to successfully graft with the scion I had.
If the blade on your new grafting tool gets dull or gummed up by sap, the cut to the scion or rootstock may not be clean and you may have to trim off some cambium that tore. Just something to consider once the tool has been used multiple times and starts getting dull.
Sorry to pull your thread off topic but grafting is a great skill to have and it’s very rewarding. Sounds like the tool has worked for others and I hope it works equally as well for you.
Simon