I've never used spray glue like 505 in fusing applique, but I have used acid-free glue sticks in pp and applique for landscape wall hangings. Acid-free glue sticks work just fine... ya know... "a little dab will do ya". You could also do the new "window" fusible method (only uses a thin piece of fusible around the perimeter, which keeps the project softly pliable).