I’ve done this on PC, and just tried it on OSX: I set up the queue, closed AE, then copied the AE icon from the Applications folder. Launched AE 1, opened the project, launched AE 2, opened the project, hit render on both. Easy Peasy. By the way, now that the second instance exists, there’s no need to create it every time. Just double-click on one icon & open the project, then double-click on the other icon and open the same project or a different project.
Now … as for working on the same comp in AE 1 while rendering in AE 2: I kept both projects open after the render. Closed queue 1, set up queue 2 to re-render to a different location. Started render on 2, changed the colour of some items in project 1.
Result: Render 2 kept going, no problems. Project 1 didn’t crash. As for the render … it looks fine, with no colour changes — so the colour changes in instance 1 didn’t affect the render in instance 2.
If I had actually saved my work in instance 1, would it have affected the render in instance 2? I don’t think so, since the instance should be accessing the project in RAM, not the one changed on disc.
Remember, if you want to use two instances to render, you must render to a still sequence. Try using the “multi-machine” settings. Be sure to select “skip existing files”.
The only problem I see is knowing in which instance you are working. Maybe if you change the UI brightness in the prefs for one instance …
Hope that helps,
Steve