I do this on my work and home account.

I seldom watch 'random' videos, mostly stick to a large curated list of channels I've grown to like over the years and I got sick of always having to remember to like or even go back to like videos (as doing my small part of channel interaction is the least I could do for them).

I enjoy all the videos of said channels (otherwise I wouldn't be watching them..).

The auto like is set to happen after 30% of the video and is very easy to hit the 0 key or - key to unlike or dislike on the small amount of videos I watch that don't deserve a like.

Pretty simple. A solution that works for many might not work for you and that's just dandy.