I use false sleeves if the dress has 3/4 length or short sleeves. They sell them at most hijab shops and there's this online place that has them in almost every imaginable colour.
Also, the boyfriend blazer has been my friend in a lot of awkward situations.
^Ooh I have false sleeves! I usually wear them with my quarter length sleeve dresses, and they're very useful in the summer time.
Also I love blazer/fashion jackets, but I still have to be careful of what I wear them with, cos they don't always suit everything.
Also, I'm really liking snoods right now, it covers a lot when worn over a hijab and makes for quite a nice look!