well, i prepare the copper board carefully before ironing the layout on it.
here is the sequence i use :
1-cut the board with 1 or .5 cm spare on the 4 sides, as heats usualy concentrate in the middle and is less at the end of the board.
2- scratch the board with sand paper, in 2 orthoogonal directions, till it brigh and shiny
3-use a clean towel and some organique solvant (i use "thinner"), and pass it on the board, each time changing with a new towel, until the towel is clean after you pass in on the board.
4-simply start the ironing process, taking less than 5 min with a 10X10 board.
5- leave the board with the paper on it in a bath of hot water for 5 or 10 min (preferably with some soab in the water)
6-remouve the paper by peeling it off, then with a tooth brush but try to be gentle using it!.
this is how i do it for more than 2 years now.
you have to adjust your printer the the maximum ink density.. (but i am sure you allready figured this out)
hope this help.