I brought my cellphone charger and cable to the workshop and dragged the cable connector over the workbench. No problem if it wasn't a magnetic one.
The connector became a ball of tiny steel scraps from the last grinder use. You can imagine how it was, because I have no picture of it, sorry.
Then my instructables spirit told me to show you how I decided to try a desperate cleaning.
Step 1: First I Warmed a Hot Glue Stick to Melt It a Little.
There was nothing I could guess would take all the steel from the contacts so quick and completely than hot glue.
Step 2: The Trial
When it was soft enough for my trial I touched the connector pins with the hot glue stick managing to push the glue all over the steel mess I made. Let it cool down completely or it won't grab the steel powder. Push it out carefully and...
Step 3: Voilá!
There you are. Almost all the mess came glued to the hot glue stick. Repeat enough to clean it all and you are done! Before using the stick again, cut off the used tip.
Just a point: There was a finishing shining sticker that came off together, but I carefully removed it from the hot glue and put it back.
Too simple to a mess so big. The cable was almost going to the trash bin when I had this enlightening, thanks to the many ingenious instructables I've seen here.