Adding and removing images to/from gift

Hi all,

after fiddling with the gift server and  add-collection I got the first 
results. That is very good.
But, after "initializing" the collection with add-collection I would 
like to know if it is possible
to add single images afterwards ( I already have an indexing workflow 
for meta-elements, primary
colors etc ) without the neccessity to run the whole indexer again.

Also, what do I have to do when I want to delete images from my 
collection on the filesystem ?

with best regards and thanks in advance,

Kamil