When finishing with Tear Away bead around a window, if you find that the gap between the casing and the drywall is too wide for the mud leg to reach properly then try using Shower Bead. It has a 1 ⅛” longer mud leg designed to span large gaps with ease, and also includes the same tear off strip to give you the clean finish you're looking for. Shower Bead also comes in two sizes: regular, for 1/2" drywall and tall for 5/8" drywall.
In the image below you can see the Tear Away mud leg doesn't cover enough of the drywall to effectively staple the mud leg.
To solve this issue, you can use Shower Bead which has a longer mud leg. In the image below the mud leg extends further over the drywall, which gives you a more stable surface so it's easier finish.