Isinglass for bottle conditioned?

Can isinglass or gelatin be used for bottle conditioned beers? When should I add it? Rack on top of it for a week long secondary?

What about my batch I plan to keg. Do I add it after I cold crash or add In my secondary? How long to leave it?

I would go ahead and cold crash your batches for four days and at the end of the second day add your gelatin or isinglass. Most of what that stuff does is cause protein to aggregate and fall out along with some yeast. Even with this there will then be enough yeast left over to cause carbonation in your bottles. Also, dont do a secondary. I would just do a primary at 3-4 weeks before cold crashing, no harm will be done. Do all of the same stuff for your kegged batches as your bottle batches.