Neglected Budgie

I'm hoping I can get some advice. I rescued a budgie over the weekend from a family member. She was not looking after it all. This budgie was living in a filthy cage (not cleaned for months,possibly even a year) it looked so unwell so I just couldn't leave it there. This bird had never been out of the cage or even outside, I don't know what his diet has been like but judging by the looks of him it hadn't been good. I will be taking him to the vet but that won't be until late this week so until then is there anything I can be doing to help this budgie get better? Here are some pics of him not the best but he is very scared and wont let me get close. His feathers are very scruffy! And is missing all flight feathers on one wing.