I struggled a lot in the beginning trying to wet the whole leaf.  I probably did it 3 times because by the time i end up in the opposite end the other one appeared to dry out.  My next struggle is getting leaf edges nice and neat, they always adjust appear jugget or rough. I'm not sure if there's a trick to make them near during wet on wet technique.  I end up using white gouache to fix some mess ups, edges and veins. Still a lot of work to do but great practice... mostly for my patience. I probably spent 1-2 hrs i  span of a week just to get where I'm. Practice makes it perfect,  i suppose.