First of all, removing grain effectively is a process that takes a very long time to render compared to other opperations. You should only remove the grain on shots that actually need it.

You said that your video about the birthday was 2 hours. Wow, it's as long as a feature film. Make sure your audience is up for watching every minute of the birthday party. If you are planning on editing the party to a short film then I'd only apply grain removal to the cut version of your project.

When you said you imported into After Effects but it only shows 30 minutes on the timeline what do you mean? How did you import the party footage? How did you set up the comp. It sounds like you need to go through the basics. Changing the length of the composition and therefore changing the length of the timeline is one of the first things you should learn how to do. The settings are in Composition>Composition Settings (Ctrl/Cmnd + k) so it's not hard to find.

First change your project settings to 32 bit. Second Duplicate the footage layer. Third, change the blend mode of the top layer to ADD. Now duplicate the top layer again so you have the original at the bottom and two duplicates set to add above it. Adjusting the opacity of the top layer will help you bring the exposure in line.

Now add Channel blur to the middle layer and blur the blue channel. Now apply Median to the top layer and adjust that a bit to average out the pixel values.

As a final step add an adjustment layer with Curves on top of everything to bring back some of the contrast. Once that's done either render the footage to a production codec or pre-compose the lot and then add your reduce grain filters to the pre-comp.

This should give you better results than just applying noise. It's still noisy, still soft, but at least you can see some of what is going on.