Appropriate time to add GCP?

[SFMapper44]

What is the overall workflow for adding GCP's to a project?  Do you need to Align Images before associating GCP's?
Also, when adding GCP's how do you know which images will contain the GCP?  I have a job with 4000 images and it would be time consuming to find each photo the GCP of interest is found within?  Does PS provide a list of images the GCP would potentially be found using the spatial data found within the image itself?
I'm a bit confused on the proper GCP workflow.

[frank.stremke]

hi
first align and reference your image set using GPS data or maybe 4 gcp in the corners
then load a list of coordinates for your gcp with the impsrt function
then select one marker after the other and use right click images by marker and only images which contain the extimated marker position are shown and also a blue flag should show aprox where the point is then move the flag to the correct point next image and so forth
frank

[Airgo]

Do I have to move the flag even if it is on the right place?
A moved marker gets green to symbolize that it is proper. Should therefor all markers be green?

[stihl]

For the optimal result (ie minimal guess work for Photoscan) means green flagging every GCP on as many photos as possible. When the flags are grey I believe they're not taken into consideration for the optimization of the tie-points. Therefor, for maximum quality you should mark all flags as green.