How dull?
For our Shun's I just give them a few passes on the strop with some stropping compound when they are just mildly dulled.
If they are more dull, then I'll either get out the stones, or if I was desperate and in a hurry, I might give them a few swipes on a fine grit diamond stone.
For a pocket knife, I've had good luck with the Lansky system which is inexpensive and easy, but not exactly quick.
Again, probably a diamond stone would be my "quick and effective"
Sharpall makes a good, reasonably priced diamond stone ($59)
https://www.amazon.com/stores/page/41D12C8E-5452-469F-B572-34B7A6035C2E
If you want something smaller, then the DMT things (and Sharpal makes something similar that I haven't tried) should work well. I have something like that (maybe DMT) but have never used them (not even sure why I bought them, but it was for something specific).
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Steve
'08 Boxster RS60 Spyder #0099/1960
- never named a car before, but this is Charlotte.
'88 targa
SOLD 2004 - gone but not forgotten