I've discovered the boom and mic in a shot that I want to make disappear. Is there a way to paste the part of the wall from a previous clip and use it to cover up the boom when it appears in the sequence or any other suggestions?
It depends on the clip as to what method you would need to employ. Such as whether there is camera movement, does the light change etc etc. I would normally tackle this in something like After Effects, BUT, if you have a suitable 'patch' clip and the lighting is the same and there is no movement, then I would suggest using the TextTool to create a feathered mask over the 'patch' clip to select exactly what you need and put this on a higher clip in the timeline than the original.