I haven't actually tried this, but I am told that "tail -f" calls fflush by default, so it avoids the buffering issue you describe.

grep's "--line_buffered" option is off by default, so these commands should not be "suffering from buffering".

I'm hoping some gurus with a deeper understanding of these issues will present the canonical way to resolve this, hopefully with a succinct explanation. I did try to RTFM on the Internet, but I guess my attention-span was insufficient to grok.

There is also an "unbuffer" command that could potentially help this situation. I Will try to RTFM at a more civilized hour.