Two or more blogs, same user database, same session, possibly different roles

I am trying to share users and sessions on
blog1.com
blog1.com/blog2

I have seen info about usermeta vs usermetashare but don’t understand the context.

I have seen info about hostsite_capabilities = a:1:{s:13:”administrator”;s:1;}
site2_capabilities = a:1:{s:13:”administrator”;s:1;}
site3_capabilities = a:1:{s:13:”administrator”;s:1;}
etc.
but don’t understand the context, where to place it and what values to substitute.

I have seen info about keys and salts, second blog referencing the first for cookies, etc. and have managed to install both blogs but have a permissions error on the second.

Some how-tos refer to modifying the capabilities file but then others say that the capabilities file has changed significantly in recent WP enough so that the old instructions on how to make this work don’t apply.

Would any of you be so kind as to go through the step-by-step, but for current WP?

I have heard that it is possible for those same users to have different roles and capabilities on the different blogs as needed. Not sure if that is possible. For now, they’d be either admin or subscribers to start.

Thank you.