I alone on the planet seem to have solved the endless problem of cleaning the fine holes of an espresso portafilter, or a Moka express fine steam filter.
None of the liquid or abrasive cleaning apps work, period.
Instead, in the past, one had to use a pin to poke out the minute holes — task so laborious and hopeless than most espresso and Moka machines in the world are hampered by limited filtration.
No longer.
The pin-holes are plugged with coffee fibre, which burns.
Place the filter over a gas flame, either side, for 10 minutes, tapping it with tongs occasionally, and bingo...
A CLEAN FILTER.
All the minute coffee fibre plugs burn or pop out.
Best to use a small coffee pot rack on top of your smallest hob gas burner for this.
And metal tongs.
Will I be knighted for this?
cooking.stackexchange.com/users/8286/Chad Evans
I would let the basket soak in a hot water ( just from the tap ) bath of Cafiza for about 15 minutes to dissolve the coffee oils.
If the problem is scale buildup I would try a soak in a citric acid bath, about 2 tablespoons to 1 liter of water.
Of course a good stiff brush could do the trick too with both the methods described here.
An old toothbrush maybe.
I would also recommend getting on a routine cleaning schedule.
I do a complete espresso machine and grinder cleaning about every 4-5 weeks
and it keeps some of these problems from happening.
Once you get into the habit of doing it and develop your own personal system it is not too hard to keep up, and you learn a lot about the internals of your machines, which can come in handy if you want to mod or need to do repairs.
Here is a pretty good how-to on cleaning the portafilter and basket link
cooking.stackexchange.com/users/6479/C.Trauma
If the clogging is a result of mineral deposits, soak the "basket" in vinegar for a few hours.
Then use a wooden toothpick to gently dislodge any deposits.
cooking.stackexchange.com/users/1092/erichui
There are special detergents for dissolving the coffee oils that are usually used for backflushing portafilter machines.
Search for Coffee Clean or Puly Caff
cooking.stackexchange.com/users/6238/groovingandi
The Chad Evans method worked.
I had no idea
how much coffee sludge
I had
that was visible at the bottom of the portofilter.
I thought this was a small rubber ring or something!
It easily crumbled out with a gentle touch with a dental tool.
I did not want to damage the finish
so I chickened out after 4 minutes of cooking over a flame.
This successfully fully opened one passage of the portofilter.
I am soaking the whole thing over night in espresso cleaner to see if that will free up the other side, but I have a feeling I will be cooking it again to free up the other side.
cooking.stackexchange.com/users/11220/user11220
I am at this moment using hot vinegar and after soaking in that for a while, adding baking soda, getting lots of coffee residue out!
cooking.stackexchange.com/users/7291/Jodi
Can anyone recommend a method for cleaning the clogged holes in a "Basket" of an espresso machine Portafilter? I had this problem with both DeLonghi and Saeco home espresso machines.  For example, in  Care of Saeco Pressurized Portafilters  (regarding  Saeco Manually Pressurized Portafilter ) they caution against using metal pins.   Any suggestions of methods or cleaning materials?
Cleaning a clogged espresso machine Portafilter
cooking.stackexchange.com
<equipment><cleaning><coffee><espresso>
cooking.stackexchange.com/questions/15952
cooking.stackexchange.com/users/6668/Itamar
You can soak it in hot vinegar for a while and then add soda, or try a bath of 2 Tbs citiric acid to 1 litre of water, or use hot water and Cafiza for 15 minutes. A wooden toothpick will help to dislodge deposits remaining. Alternatively, you can place the filter basket over a gas flame and tap it with tongs occasionally. You can place the filter over a gas flame, soak it in hot water or vinegar.
Place the filter over a gas flame to clean it up. Soak the basket in hot water or vinegar. Use a wooden toothpick to dislodge the deposits.