The standard way is to the Daunjoch Chairlift, get out and out the skins on. If the snow is firm, you can even just bootpack but you do need full glacier gear for this one. Get up to Daunjoch. Alternatively you can also get in from the Daunscharte T-Bar. The entry over the ridge is generally more challenging and at times wind-affected.
From here an amazing, not too difficult run awaits all the way to Gries, and further in great snow conditions. Ski down the first step until you reach the wide open Sulzbachferner. It hardly ever gets tracked, there is tremendous space, but there is also crevasses, so ski carefully, going it alone has a spiritual feel to it, and is reckless.
Blast down, route finding is obvious now. Pass Amberger Huette, down to Sulztalalm always following Fischback until you hit Gries.
Usually Taxi pick-up from here is best, sometimes you can go further but it get very flat until you reach a short patch shortly before Laengenfeld where you can ski along skiers left of the valley. Attempting to go down from Gries only really makes sense if you stay in Laengenfeld. If you are up in Soelden anyway, you win little.
There is a two other, less exciting runs towards Soelden, one way via the Windachferner. Just follow the fall-line from the Wildspitz Chairlift. The slopes are sun-baked and rocky, especially lower down. The other slightly better alternative is to follow Gaisbach from the bottom of the Pfaffengrat Chairlift. Same as a above, the snow cover can be mixed.
For both variations once you reach the valley floor follow the trail to Soelden. The latter two are not all too great, but will do as a nice adventure not too late in the season. If you need to get over to Soelden from Stubai in white out and can’t be bothered with the long drive, the last one is the easiest to navigate.