I often find that deblocking filter barely makes a difference or does not remove the macroblocking at all whichever setting I use. So I must be doing it wrong. 2/10 times it will work after a lot of test encodes of a few seconds and deblocking will work. But most of the times it doesn't.
How do I estimate which deblock settings to try. When should you use small(4x4), medium(8x8), large(16x16). Does this correspond to the size in pixels of each macroblock in the source?