It's fine to backpedal while standing.
My suggestion is just to ride more. Eventually it wil get easier.
You can try and gear down by getting a larger cog, but sometimes this can make it tricky to backpedal when spinning very fast.
Since cogs are inexpensive, it doesn't hurt to try and gear down.
Also, having good, solid foot retention helps slowing down quite a bit. What are you using right now?