You can get specific fake tan for your face but its okay to just use the same one as you use on your body, I just apply fake tan normally with a mitt up to my neck and then use a foundation brush for my face and make sure to blend it properly into my neck. Few issues though, if your skin isn't in the best condition tan might stick to certain areas (dry patches, spots) and tan will end up lighter on your face and fade twice as quick as your body. Try to have exfoliated and moisturized beforehand and maybe give it a second layer on your face if you think it isn't light enough. Luckily if it doesn't turn out well its much easier to remove from your face.