Obviously, break with the 6. The 2 is a good key ball, but there is no easy way to get on it. If you are going to play it in either side, you have to be in a very narrow shape triangle unless you plan to go one or two cushions to the ball.
Is there a way to play the 2 to a corner as a key ball? Again, it is so far from the pocket that you have to be nearly straight in (and on the correct side of the ball) to use a corner pocket. The 7 is a possibility to get on the 2 but working backwards from there doesn't suggest much.
So, for "key balls with cushions" we have the 1 and go one rail or two out of the top left corner, the 4 and two cushions out of the top right corner or the 9 and one rail off the top.
The problem with the 1 is that you should play the 7 just before and you need to get good position on the 7. This could be done with the 8-7-1 with minimum motion by playing the 7 in the side. If I get just right on the 7, I'll leave a draw shot from the 1 and not use a cushion. You can start with the 2 (one rail), 4, 9 to get on the 8.
If you're not comfortable with that sequence for the 1 as a key ball, you can start wtih 8-7-1. If you screw up, you can recover with the additional balls on the table. Whether you use the 4 or 9 as a key ball after that depends on what your shot on the 1 is.
As a final wrinkle, if the 1 is a favorite key ball for you, and you end up with the right angle on the 7 after starting with the 8, you could go up-table for the 2 and 4-9 or 9-4. The big advantage of the 1 is that it can be shot from a lot of different angles and you can still get a good angle on the 6.