Writing female characters come easy to me, you develop their personality and roleplay as them... gender doesn't really come into the factor. To me, it is almost literally aesthetic.
It can create some writing conventions based on gender but other than that it just falls into the background unless you're playing someone who flaunts their sexuality a lot, but even then, you're making the character sexual, what assets used just comes down to what they have, the important part is that the character is sexual. Body is just the convention of emphasis and story options, if you want to play someone who is massive, strong and masculine, male will emphesise it more, female will give some interesting story options but neither really effect the characters theme.
Always weirded me out that some people have a lot of trouble with it.
-shrugs-
Male, female, both, neither, 2 feet tall, 15 feet tall, humanoid, monstrous, corporeal and incorporeal and all of the above, I've done it all and its all the same.
The only difference is the character and what you want them to be and what will fit thematically with that character to better tell your story