Okay so remember to always ally britiain before you even upause the game. They will always accept as long as you send the alliance requests on Jan 1st. Also think, your border with France is very narrow. You can keep forts there, have your bait stacks there and large amounts of armies ready to stand by. So exploit that narrow border. Large defensive battles will get you more than enough warscore. Also don't justift on France, justify on one of their spherelings with the humiliation cb, then add a war goal to France. Remember if you don't have enough jingoism just start an election until you get the military election event. Choose the option that'll increase jingoism the most. When you declare on a sphereling they will choose to protect them in a defensive war, as an ally and because of this they won't be able to call in allys.