TBH mate you would be better off not using cellulose its not as good as it was years ago as they have taken out much of the lead contents etc out.but 70 - 30 will be fine if you have made up your mind and use topcoat thinners and NOT standard. as for times between applying coats it will totally depend on the enviroment you are spraying. are you doing it in a proper booth with a oven to bake when painted???

from past experience 2 pack paint is better all round for that real good finish good luck send some pics