I brewed an oatmeal stout yesterday and would like a creamier mouthfeel. How much lactose would be appropriate to add and would it be better to add at bottling or when it gets moved to secondary??
Personally I would add it at bottling time. Make up a boiled solution and after racking your beer to the bottling bucket add it slowly in batches and stir it in, then give it a taste test. It's easy to over do it so you want to be careful.
Unfortunately I don't have any answer on how much to use, I've never used it to add back body.
I just a lot of looking around on that and most recipes used 1/2 - 1lb for 5 gallons. A good mental reference is 5 gallons of milk has a about 1.94 pounds of lactose. Give the raw lactose a taste too as it's probably a lot less sweet than you might think.