The goal of gooning is basically to masturbate for infinity riding the edge before the point of no return. You're going to want a lot of time and probably privacy. A good goal for starting off would probably be an hour, extending the duration as you get more good.
Personally I like to get stoned AF before going at it. Lacking weed, alcohol is OK but only in moderation because too much and I just get tired and sleepy with a soft peepee.
Some people will also talk about these "Poppers" things which you sniff but personally I would not recommend as I like to stick to substances scientificially proven to not end my life too soon. It tends to be sold as VCR head or leather cleaner apparently. Additionally its like way harder to get than weed here so fukkit.
Then the next step is to pick a few videos. IMHO the best videos are ones that can loop without being too jarring as to be obvious that it has started over. You'll want videos that do not have annoying title slides, ending slides, or the scrolling garbage text from shit sites like xhamster or erosclips. The videos do not have to make sense, just be visually interesting to you in some way.
The two that have the thumbtack in the top right corner have been pinned by DeskPins such that both of them will always be on top of the third video.
Maximize each video, hit play, then use PeekThrough to make the two that are pinned also be translucent. Here is an example video recorded using the shit built into my NVIDIA graphics card:
You can also have the pinned windows just always be an overlay while you're doing actual work. This is a screenshot of a where I'm extracting, cleaning, and stonerifying the audio from PF's Good Boy Goon used in the video clip above.
VLC can do a lot of things on the fly so that you can remix your own goonsesh without having to break out heavy video rendering tools like Premiere and AfterEffects.
Tools Menu > Effects and Filters.
Here are some examples. Keep in mind all these filters are applied on-the-fly live, so the more filters you add the stronger your computer will need to be.
VLC has the ability to repeat videos on loop, but also to loop only a specific part of the video. Here is one where there is a fade-in from black at the start and a fade-out to black at the end and I want to skip these fades while gooning out.
View Menu > Advanced Controls. For some reason this only shows up if VLC is a window, not when it is maximized. This adds a new row of buttons above the play button.
In this case I just skip ahead to when the fade is over and she is between statements and then click the Segment Loop button. Then I skip to the end just before the fade and click the segment loop button again. It will now repeat only that portion of the video.