An owner could flush and bleed a hydronic baseboard system if the owner knew how the manufacturer required the system to be flushed and bled.
Your boiler’s manual should provide that information.
But if this is a long existing system,it is more likley that the ‘automatic vents’, designed and installed to continually ‘bleed’ air from the system may have failed, and need to be replaced.
Either way, the fix is cheap and you would do best to simply call a professional for this one.
It will save you time and frustration imho.