I am new to this and find this the only part I really struggle with, please elaborate the details of your method.
Sure, I'll help what little I can tell from my own experience from trial and error. I use toner transfer with chemical transfer, NOT heat transfer.
1: With laser printer (no, you can't use inkjet) print pcb layout using as much toner as possible on glossy paper. Glossy because we want as much "excess" toner as possible on surface of paper instead of toner sucking in paper.
2: clean pcb surface with acetone, but before that, scratch surface bit with sandpaper. I get better results with sandpaper than steelwool/similar. IIRC I use 240 grit paper, just nought to make better contact for toner to stick. After scratching, clean copper with acetone & soap/alcohol to remove copper dust as well as any other dirt on surface.
3: Now to apply toner, apply acetone evenly on cleaned area, then place print on it. Wait while for acetone to soak paper, then apply ONLY vertical pressure to press print firmly towards copper. Acetone now has diluted toner, and when it is dried, toner has transferred to copper from paper. Now, DON't try to peel paper off when it's dry, mask is more fragile than it might look (actually you shouldn't see any toner, it looks now like you'd glued paper on copper)
4: Now to remove paper from copper but leaving mask intact. Pour very hot water, (boiling can be too hot) but what you can get from sink is enough. Let copper+paper combo be still in water for about 5 minutes, forget it you could say. Now, under water, peel paper off SLOWLY and GENTLY, no brushes, fingers are enough. Try to peel it along tracks, it tends to be better that way.
5: now you have pcb ready for etching. I use Vinegar (10%, grocery store))+hydrogen peroxide(3%, pharmacy) combo+salt (grocery, must be proper salt, nut potassium stuff)
Ratio is 50/50 vinegar and hydrogen. This is enought by it's own, salt is used to boost effect further. BUT, I highly recommend heating etching solution (40'c degrees is enough) as well as using aquarium pump to deliver fresh air as well as keep liquid on constant movement. With this method etching takes no more than 20 minutes, and no rubbing needed. This took 30-40 minutes:
To see how etching process goes on, look on copper side to some light. Also when you see gunky stuff on copper surface, shake pcb bit to clean surface (oxides or something form in copper surface).
when applying salt, teaspoon are mostly enought, pour it on copper surface and reaction goes like crazy, it can frighten bit, there can be very much bubbles.
After process is done, clean toner with acetone and now all there is left to do is drill holes for components.
Etching solution afterwards is hazardwaste, it contaisn copper salts (sulfate) that is poisonous. But boy it is one good electrolyte to use, it is afterall copper diluted in salt-water
.
I think that's all.