I think what Chris is trying to say is the grainy results you got might be because of the vagaries of expired film (storage conditions, how long past expiry, etc). If you try again with fresh film, you might get more satisfactory results, or at least have eliminated one variable.
In any case, I used HP5+ with Compard R09 several years ago, which I believe is a Rodinal clone. Like you, it's what I had so I used it. I didn't love the results, but I didn't hate it either. I used 1+50 for 11 minutes, metering for the shadows using the M5's semi-spot meter. Ignore the slight distortion at the edges of the frame, I was also using the Canon 50mm f/1.4 LTM as my digitizing lens at the time.
Leica M5, Canon 50mm f/1.4 LTM, Ilford HP5+, developed in Compard R09 at 1+50 for 11 minutes.

2016.03.12 Roll #069-09260-positive.jpg by
dourbalistar, on Flickr

2016.03.19 Roll #071-03-35.jpg by
dourbalistar, on Flickr

2016.04.09 Roll #073-09326-positive.jpg by
dourbalistar, on Flickr
Here's one that came out quite grainy with blocked up shadows, but I used a M39 pinhole body cap on a Cosina 107-SW (aka Voigtlander Bessa L)
😀
Cosina 107-SW, M39 pinhole body cap, Ilford HP5+, developed in Compard R09 at 1+50 for 11 minutes.

2016.04.24 Roll #075-09286-positive.jpg by
dourbalistar, on Flickr