Yeah I had alot of this thoughout my career as an athlete. I can feel it now right through my back, glutes and hammies when I stretch them out.
The ‘flossing’ is a good start then using the various stretches. If you PM me with your email I will get some stuff to you. Im not a physio but just experienced this alot.
I have been talking recently with a physio I work with about the tension being made worse through mental tension/stress. For example I coach a guy who when he is stressed (normally during the January tax return period as he is in accountancy!) he gets all sorts of spasms so we have learned to adapt the programme to suit and make sure we dont overload him any further. same happened during girlfriend trouble etc.
There is a physio here in the UK called Martin Haines who has developed a 3 stage course one stage deals alot with neural tension. He described the nerve tissue as much like the plastic you get round a six pack of cans/beer etc. If you pull it hard/fast it wont stretch as well as when you tease it out more gently. This was useful info to take on board for stretching procedures.
I have got to the point where all I do is a few neural releases in my warm up and everything else feels loose too. Definately something to get on top of.