Navigating collaborations as a postdoc I am a new postdoc (finished my PhD a few months ago) who started with a new group during COVID-19.
In my field collaboration is the norm and solo-author papers are rare. I need to start approaching people (both within the group and external) to collaborate on projects, but I am very nervous, and even after reading several existing questions on approaching collaborators I am not sure what to do.
There are two professors I might collaborate with. For each scenario I have also included some specific questions in bold to address the things I'm struggling to figure out.

Working with a professor in our group who has a very impressive track record in creating new methods/tools. I have an idea for a method that could build on some of his work to address a different problem (about 30% his existing code/method and 70% new things). He liked the idea when I met him a year ago during my postdoc interview, but I'm not sure if he knew that none of my prior experience involved developing new methods. I would probably need a lot of help/guidance on this.

He is friendly and approachable with PhD students, but I'm nervous because as a postdoc I'm not sure how much help/guidance I'm still allowed to need. How should I go about approaching him, and what should I say to define potential roles/how the collaboration would work?

A professor at another university I have previously exchanged a few emails with to ask question that fell within his area of expertise (my postdoc mentor introduced us). I am thinking of doing a paper that builds on my dissertation using a different type of data. He wouldn't be familiar with the method I'm using, but he is very familiar with the question and the literature, and I could use his advice on different ways to define/measure the outcome in the new data. The reason I want to invite him as a co-author (if there is a paper) is because his expertise would be helpful for the discussion section, and once there's a paper draft the whole thing could benefit from his input.

It may or may not be possible to do this paper - I can't check statistical power until I ask him more questions about defining/measuring the outcome. When and how would it be appropriate to transition from asking questions to inviting him as a co-author? And what should I say (and when) to discuss defining what his role as co-author would be?
Note: answered before recent edits. I'll clean it up after it settles down a bit. (minor edits made for temporary readability)
In all of these questions, don't try to settle all issues at the outset. Just start a dialog. In the first case, admit that you will need his help on &quot;methods&quot;, but that you hope he is interested in moving forward with you on the topic.
In the (now removed) case of a student suggest that you are aware that there are issues about his ability to commit, but let him decide whether to spend the time and effort.
And in the second case of a remote professor, ask for his willingness to give you feedback and perhaps collaborate on a paper.
But the key is to open the conversation, not to write a contract. While the boundaries need to be made clear fairly early in any collaborative effort, it needn't be the initial concern. And, most important, don't make assumptions about what is possible before you ask.