PCBgogo

I needed some quick PCB's, so I played a little with the Brother laser transparencies:
Printer = Brother HL-2270DW
Printer settings: HQ1200 ; Advanced>Other Print Options>Improve Print Output>select Improve Toner Fixing     
Transparency: 3M CG3300
Program: Eagle 7.2.0
The problem with Brother's toner (and probably other low-temperature fusers too) appears to be that the toner is soft relative to HP's Laser Jets.   Microscopically HP's toner appears as relatively small dots; Brother's appears more blotchy like fine ink splatters.  The process of going over the transparency liberally and then wiping the dried marker off left scratches and removed some of the original toner.  On redoing it, I became suspicious that most of the damage happened while trying to paint on the image.  Also, according to the MSDS's, it appears that the different formulations all contain a relatively high boiling solvent like 2-propoxyethanol (aka a glycol ether, "Cellosolve"
So, here is what I did:
1) Removed ink cartridge from the maker and squeezed out the ink.*
2) Used a small, round camel hair brush to paint a thin layer of the ink onto the printed transparency.
3) Use a hot air gun (low temp space heater) to thoroughly dry the solvent before wiping the excess off with a soft tissue.  
4) (optional) I added a very small amount of isopropyl alcohol to the ink to get a thinner layer.  The thinner layer is easier to remove, but putting less ink on the brush also works.   A brush wetted with alcohol was all that was needed for 2 mL of ink.  Too much diluent will ruin the ink for this purpose.
Attached photos:
Brother PCB 020317 #2: Image with view box (fluorescent bulbs) back light showing difference between treated and untreated areas.  Unfortunately, my camera had a tough time focusing because of the inherent flicker of the lamps. 
Brother PCB 020317 #3: Magnified image with an Adonstar camera

After thorough drying, I found the Brother toner just as durable as the HP toner.  In fact, you can polish the image until no more black marker ink is removed without damaging it.