I've been using 220 grit sandpaper per your advice...since a year ago?
Then I used acetone to clean up the fingerprint oil and sanding dirt.
Not that fingerprints are a problem... I always wear heavy 9mil nitrile gloves when playing with PCBs.
Is the iso-prpyl wipe anything more than or different than using a tough paper towel and 91% alcohol?
I had experimented with transfer craft metallic foil but really didn't need the foil after using a Sharpie.
I can see using the foil for massively complicated or detailed circuits that would test patience tracing a whole board with a Sharpie. But nothing I do is that complicated.
Genuine or non oem HP toner works for me. For the pitting problem I
transfer craft metallic foil on top of the toner before etching. It's a
well known practice and reliable.
Rather than using acetone or citronella to prepare/clean the copper I
use 220 grit sandpaper and an iso-propyl wipe which makes the toner
'grip' the oil free copper. Even fingerprints can interfere so handle
the edges of the PCB. As a test I polished/lapped copper and tried the
identical transfer with poor results all other things being the same.
Also, before I did the metal foiling, I used to use a silver sharpie to
'fill' in the toner transfer for any breaks or potential pitting and
then etch.
I have done literally hundreds of double sided boards and even boards
for RF use to 1Ghz with toner transfer. It works.
Ancel