EIn doesnt have the best moves on approach but run up sweep, run up H+K, run up grab or 66T has worked for me. So has starting P and 1K strings at the right ranges.
I don't like 66K approach because I feel its easy to hi counter blow approaches like those. Also you'd be better in the MU if you were more familiar with Ayane's range. You stayed full screen at times which doesn't encourage her to do much and limits what Ein can do because if she whiffs something chances are you aren't in range to punish it.
If my intent is to hang back a bit I tend to stay just outside of 236P / 46P / 6P+K range. That way i can respond appropriately. If I see strings being started from range I can hold 4 and step back to retaliate with the appropriate whiff punish if there is enough space.
If not I can just hold guard and stay safe. My actual judgement on this isnt the best as there have been times i 46P into getting myself counterblown but its worked for me more often than not.
When Ayane rolls our options are 1K, 4K, 236P. I tend to use 1K, 4k more because 236Ps hitbox isn't all that good for a mid punch. 4K is landing on counter or hi counter most of the time. same for 1K.
If you stay just outside of 236P / 46P tip range Ayane only has drill kick, 66KK4, and possibly 3P as options to come in. I need to take a look at 3H+K but id say it has around the same range as Hitomi's 46P. Everything else is whiffing. 66KK4 might be avoidable in some instances.
Another thing I have to say is dont be afraid to abuse or get predictable with 2P. You tend to do it once and go into a move intended to counter blow such as PKK and 3P. Our strings are pretty bad but we gotta use em. PP2K, PP6P and P / PP cancel pressure. 6K to take the heat off 3P.
Even when it gets held do it anyway. If you have them holding it means they are thinking about it more than they should and you can open em up hard with the mids and other options.