Dry hopping technique

From what i have heard it is best to dry hop @ about 90% to your terminal gravity so the yeast can take up any oxygen inadvertently introduced.When doing this the co2 produced by the yeast keeps the hops at the top, even when dry hopping for 10 days @ about 68-70F the majority of the hops seem to stay on top until I crash cool then they drop. So why when i hear micro brewery's speaking on this they are concerned about rousing the hops with co2 to keep them in suspension (off the bottom)? What are they doing different to get them to sink?

You are using an old approach. Most of the time dry hopping is done after the fermentation is done, often just before bottling. Done later, the hops sink.

I put my Centennial pellet hops in a strainer bag with a couple of marbles to weigh it down. I used some Saran Wrap tied to the bag then draped that over the carboy neck and re-installed the bung. I'll know how well it worked in about 10 days.

still here brewers talking about this method to this day, I heard Vinnie from Russian River still does Pliny this way IDK?

its not really good idea to dry hop in primary on yeast. Yeast will absorb some of that hoppy goodness aroma and CO2 from fermentation will strip it away even more. For that reason I dry hop only after as much yeast removed as possible. I gelatine first than dry hop.

I was going to try this technique for the 1st time next month. I do have a question, do you add gelatin to the carboy or rack to a secondary (or keg), cool, THEN add the gelatin?

I'm thinking about racking off the primary into a keg and cool for about a week @ 45F. Then add gelatin and wait 3-4 days...then add the hops in a bag for 10 days.