Even the inkjet water decals works pretty well. I did all my football minis decals myself (on transparent and white decal paper).
The transparent decal sheet (mostly used for black decals only) are the easiest to use.
The white background are a bit more complicated (you need to know the exact background color for perfect blending, and the borders "bleed" a bit of ink too, so you'll have to fix some defects then).