I find it pretty simple to input actually. I just input it as F22.
If you want to make it easier you can change your controls settings and change Input Window Timing to Long . This will provide a longer period for you to input the F22 than normal, which inherently makes the ability easier to use.
In comparison to stanky leg its night-and-day easier, but considering with practice I found it pretty simple and reliable to get consistent Stanky Legs working on MKX, I don't think F22 is that big of an issue.
Just gotta put in that time in the lab.