I use and love the oglow,it's so easy to use and doesn't cause any problems at all over the top of foundation as you really only need to use the tiniest amount of it. I have heard people say to apply it with a brush, and I do apply all my makeup with a brush apart from the oglow, i find it is easy to apply too much using a brush. I just put a tiny little bit on the end of my middle finger and sweep it along the apples of my cheeks, it's quite a thick liquid and as I said as you only need a tiny little bit it won't interfere with your foundation at all.
I have applied it over foundation and under halo, over foundation and halo, under just halo, and over just halo, and on bare skin, and it always gives a wonderfully natural look. I hate overmade up looks, especially too much blusher, and this is perfect for me as it really just gives the merest hint of a natural blush. I was disappointed at the size of the tube when it first arrived, it was so tiny, but it lasts aaaagggggeeeeessss!!!!!