Bulk Oxidizing Agent PBW or Similar

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Which is what I linked to.
The OP (original poster) has two kegs with an option of another two, Oh that's 4, so CIP (clean in place) could be relevant, in this case it's not but you should read the thread before commenting on a single post.
Assuming people are physically able/inclined to roll 50L around may be your opinion, but you know what they say about opinions.

Sorry I didn’t read through the whole tread, does it go on to describe how to clean a keg with the spear removed? I wasn’t suggesting rolling 50L around, just 3-4L in a keg.