pitching on yeast cake aeration

I usually aerate then add yeast. When pitching on yeast cake should i aerate the wort first or is it ok to aerate the beer once dumped on the cake. What are your methods for doing so? thx

You probably don't need to worry about aerating you wort much at all if you are going to be pitching onto a cake. The oxygen in the wort is primarily needed for yeast reproduction and if you're pitching onto a cake from a low to moderate strength beer, you will probably already have a large enough population to ferment the wort without any further population growth.

You should however be aware that pitching on a cake is only reasonable if you are using a neutral yeast such as wlp001, wyeast1056 or US-05. If you are trying to produce something that should have a good fruity ester profile it is quite likely that this will not show up in the finished product as ester production occurs mostly during the reproduction phase.

I have tried this a few times and I would not aerate if you are pitching onto the whole cake.

Unless you are going to a higher gravity beer, you are typically better off washing the cake and pitching 1/3 to 1/2 of it, and aerating. It is beneficial to get some yeast growth; without growth you have tired cells doing the work, and it can cause off flavors. (I know this from experience...)