I just cup them in my hands and blow gently. Not with my mouth right on their beaks but with the hand enclosing the bird and the breath. Then (if you need to know this...), they go into the bra in the cleavage for warmth... then more puffing til they are better. Really!
If the little bird is infested with red mites......you might not want to put it in your bra...... Rubbing your palms together very briskly for a minute will heat the palms and you can cup the bird in your hands to warm it.
Oh they do carry little pests on them. Sometimes they dust the eyases for mites.