Here's a trick

You find yourself filing and stoning things when you make a 1911.

Some time you want to file more on the left side, something the right.  Assuming you are filing with your right hand and you want to angle more to the left, life your right elbow higher than the work in the vise of fixture.  Drop your elbow to favor more removal from the right side.

If you want straight on flat and you aren't quite getting it.  Say, when stoning the sear, raise your shoulder up.  It makes for a flatter straighter stone stroke.

I swear, if you want to do a 1911 right, and if the class existed, I would recommend a 3 month long course on the fine art of hand filing before touching gun parts. 

And a one month course on dremeling.