I reckon about half my customers are both sides and I automatically do the out and then the in...but I now wonder whether this is really the sensible order because:
1) The number of times I've struggled to get at a window from the out and then find that when doing the inside I could have simply opened the window and done it from there.
2) From the customers perspective: You're doing the outside...they know you're eventually coming in....and they may fancy making a private phone-call to their lover...watching their favourite soap....a nice smelly poo to jettison last nights chicken vindaloo

...etc etc....
But they can't really cos I'm gonna be in any minute. If you do the inside first you're out of their life and you can piddle around with the outside to your hearts content!
3) And the most important....as KJG so rightly says
Insides first so I can see what I can get away with on the outs 
I've talked myself into this....gonna give it a try!