Coaching takes many forms. Face-to-face tends to be the most effective (and often the most efficient); however, remote coaching can also work. Here's a glimpse into my mailbox showing an example coaching response to a followup question from a Product Owner with whom I have been working.
Subject: Scrum Question
Your email reminded me that I was going to ask you a question.
We have a project that has 3 teams now but will likely have 5 in the near future. Today we are using Excel for the Product Backlog. But we are over 500 items and maintenance is very hard.
Are there any tools your recommend for large projects?
Subject: RE: Scrum Question
Regardless of the tool, 500+ items are going to be a bear to maintain. A key practice is to keep the queues short. Some questions back:
Why is the backlog so big?
Are all these items worth maintaining on the backlog?
Can the lower priority items be off-loaded to a separate list (i.e., parking lot) with promotion to the active list deferred until the item becomes timely and important?
If you have a parking lot list, is there actually value in maintaining this parking lot or will the items surface if needed?
Could the "project" be decoupled such that each team is handling a sub-system with its own (smaller) backlog and a scrum of scrums to manage interdependencies through "service contracts"?
Rather than change tools, you may want to consider:
How can we reduce batch size for each release?
How can we reduce batch size for each team?
Current research is showing that smaller batch sizes result in more frequent delivery and higher reliability. Is faster feedback and higher reliability worth the investment in figuring out smaller batch sizes?
Also, a smaller batch size may eliminate the need to migrate from your existing tool. Then again, if Excel is insufficient for other reasons, experimenting with other tools may be worthwhile.
BTW, moving to a new tool capable of maintaining a larger queue will likely result in a larger queue. Is that a desirable outcome?
Regardless of format, coaches ask a lot of questions. It can be easy to give a pat response or recommendation. It is much harder to figure out the right question. In Rob's situation, the better question is whether the queue is the right queue rather than which tool to use.
Is your coach asking the right questions?