Hi Ian,
My printer is a HP Photosmart C4385. For printing the decals the only changes I made was to select highest quality and 600dpi, I have gone as high as 1200dpi but I couldn't notice any difference. I also did a few diagnostic checks by first;
Align print cartridges
Clean print cartridges
Calibrate colour
Print quality Calibration
This makes sure that everything is running correctly with my printer and that colour calibration is where it should be. Every printer operates at different settings so to compare one brand to another is a little difficult.
As far as normal or gloss paper, my printer is set for plain paper, I did at one stage select photo paper but it didn't make any diference to the quality of print, just used heaps more ink. It is important to check your own printer manual and go through the settings available, experimentation might the the key role here. It took me a little while to get my setting right but now that it prints okay I don't touch it. I have a continuous inking system on my printer so I never have to change or refill the cartridges, printing costs are cut by 90%.
Des.