I don't build SSRS servers very often, far less than SQL Servers, and I haven't created a build doc for SSRS 2008 (R2) yet. The install I did was to test if our reports worked without any issues. As far as I know setup and install is pretty easy.
I'm obviously an admin on the actual box and syadmin to sql. All the connections and setup use integrated security, Everything runs as domain service accounts.
You should be able to step through the ssrs config from management without errors - you set permissions there. I don't know which o/s you have but windows 2008 r2 introduces a few changes from windows 2008 some of which are very annoying! Lookout for windows firewall ( which claims it can't be disabled in R2 ) allowing remote access for both o/s and sql.
I usually work on the basis of:-
can I rdp to the box
Can I map a drive/share
can I copy a file
Can I register sql and ssrs in SSMS on the box ( or in rdp session )
can I resgister sql and ssrs froma workstation.
can I get to ssrs locally e.g. localhost/reports or reportserver
can I do this from another server/workstation using the server name and the ip address ( which may need a login initially )
hope this might help