The other streches are important too, don't ignore them. Stretching regularly maybe the hardest and most valuable change you make. Stop doing the things that shorten the back of your leg. Probably you spend a lot of time sitting in a chair. A little stech done very often will make a big difference.
Massage is great for loosening muscles.
There are several different massage modalities that are myofascial release. Adjust your cockpit fit. This will give some slack in your posterior leg. Don't let your low back slouch down. Sit up right on your sits bones.