I have some video footage in Premiere that I wanted to add some effects to in after effects so I right click on the timeline and replace with after effects comp. I add the effects and its all good but what if later I want to add some more to the same clip. I though I would just open my project in premiere and open the linked file in after effects and add but it doesnt appear to work this way as the new effects I m adding I cannot see in premiere. So I though perhaps I have to once again replace with composition but this doesnt work either and all I get is a coloured blocks image like a test pattern. How do I do this?
You need to make sure that you've saved the AE project, that nothing has moved, and that you use Edit Original in Premiere to get to your AE project. That should be all there is to it.
You should also be able to simply open the After Effects project, edit that, and save it. The next time you open Premiere the changes will show up.
The only way to break the system is to click on your Dynamic Linked footage in PPro and select Replace with After Effects Composition. That will create an endless open loop where AE is looking for a project that is either already open or trying to open another aep file that's already open. It just won't work. Edit original will.