Yes just before cold crashing works for me but here is a copy and paste from a beer journal.
Adding Gelatin to the Beer
There are different schools of thought in regards to when to add gelatin to your beer. Personally, I prefer adding it to the fermentor during the second day of cold crashing prior to packaging, but others may add to the keg prior to serving. There are four main benefits to adding gelatin to the fermentor. It allows brewers who bottle their beer to enjoy the full benefit of gelatin fining, and it removes any further work after packaging. It also gives you a clear beer to rack to the keg so as not to have additional trub to suck out of (a possibly clog) your posts or lines. Finally, it eliminates the possibility of introducing new oxygen into your brew post packaging. But, as we all know, sometimes you forget or you have none at hand during packaging, so the option to add to the keg is there. If this is done, be prepared to suck a good bit of sediment (a pint or two) out of the keg prior to getting to the clear stuff.
Either way, the beer must be cold (34-40 °F) when fining with gelatin. I let the beer crash for 24 hours to drop out the main sediment, then gelatin fine for another 24 hours to allow the very fine sediment to drop out. I do the same regardless of kegging or bottling, as fining with gelatin will have no negative effect on the yeast in suspension needed to bottle condition/prime your beer.
Obviously a American journal with the spelling of some words but do whichever you think suits you as I have said I add just before crashing and it has worked for me
Ps I very rarely Fine my beers nowadays as they do clear pretty quick generally or I make hoppy beers which have a slight initial haze but do clear overtime (I do not fear the slight haze)
