Yes, support is your friend. It's hard to watch the chisel, and also keep it flat and level. The plate is flat, or very very close to it, so to have waves like that it's you moving. doing backs, allowing the chisel/blade to just lay flat will get you there.
On anything that will fit into it, trust the chute for your bevels. It will keep you at your selected angle, and is also as true as you could ever hold it simply by allowing the chisel/blade to rest. Moving forward slowly will engage you into the disc.
Always think Baby steps, trying to go to quickly will usually end in rough results.
Basic video to hopefully make you more comfortable with it. Plus if you have a beater chisel it can allow you to relax a bit and get it done, not thinking about good chislels.