Burp a sleeping baby?

Any special tips or tricks to burp a sleeping baby? Little one is 8 weeks old tomorrow and has started to hold on to her gas during the night 🤦🏻‍♀️ I can spend up to a good half an hour trying to burp to no avail. I eventually give up and put her back down. She squirms a bit and eventually falls into a deep sleep. She then won't bring anything up in the next feed either ... This morning she did a huge burp and then threw up all over me which is something she's never done before. I don't want a repeat if possible!