I am struck by how quickly we choose to take the easy way out, such as being rude to drive him away, or being kind but then ignoring him, or pretending to be deaf so we don't have to relate to him.
The reality is that this neighbor is behaving inappropriately, causing stress in his neighborhood, but nobody seems to be holding up a mirror to him so he can learn and change.
I think the solution, if one is courageous enough and actually wants to create change, is to state how his advice is making you feel and perhaps to offer suggestions as to how he might approach people if he'd like his "advice" to be received more positively. You could even be playful and have him practice a few introductory words you've given as an example, such as "What a great job you are doing." (Start with a compliment.) "When I was doing a similar project I learned some tricks that I found very helpful. Would you like to hear about them?"
As he tries to practice these with you, you can point out if he's sounding too pushy, and you can also prepare him for the answer of "No, I'd rather not hear about your tricks right now."
Ideally, there would be self-awareness on his part and a new understanding and relationship between you. He may decide not to pester you any more, but the basis of this would have been good communication with a desire to understand each other instead of a blunt deterrent.