Don't know much about "proper" de-stressing techniques, I'm sure there are loads of people on here who do, but I used to be in quite a stressful job and these are some of the things I did:
When I left work, I often could not stop thinking about it. So what I did was give myself a time limit. So I'd get out of work and I'd say, "right Mossy you have 20 minutes," and during that thirty minutes I'd give myself permission iyswim to worry as much as I wanted. When the 20 minutes was over I'd make myself stop thinking about it.
The 20 minutes usually coincided with the length of time it took me to walk to the station to get the train home, so what I'd do to stop myself thinking about it was to make sure I always had a really good book with me, nothing too challenging, just something I could really get stuck into so I could forget everything.
I found that a lot better than just listening to music, with that, it's far too easy to "switch off" and think about work instead.
If your dh drives, he could do the same by getting an audiobook?
I did find at times I was drinking too much as a way to relax, so other things I did to try and relax in a different way were:
Hot bath
Long walk with the dogs
Jogging around the park
In a similar way to what I mentioned above where I gave myself 20 mins to "worry", I also would try to avoid boring dh too much by going on about what had happened in work that day. So instead, I'd have a brief chat with him (and vice versa, he'd share his day with me) and then we'd talk about something else. So we'd make sure we'd read the paper of a day and then talk about the top stories and what we both thought.
(That makes us sound really boring I know!)
And really important is he needs to make sure he gets (1) enough sleep and (2) enough sunlight. If it is a very stressful job then he is probably like I was, not really "allowed" to take even half an hour for lunch. But even a ten minute stroll round the block at dinnertime in the light is better than nothing.
I used to allow myself, once a week, to take a full half hour for lunch, and to make sure I got outside. Also twice a week I would make sure I left on time.
I hope this helps, grief I've gone on a lot, I'm sure someone here will have "proper" stress relieving techniques but these are what really helped for me.