I used the spray glue also.
I stapled 1 end first then spray glued generously and then put down the leather and then used a rolling pin - then stapled the far end.

Right after it was laid it looked great. 4 hours later there were air bubbles then when I woke up in the morning everything was flat and smooth. I was working in my friend's cold garage when I applied the glue which may have caused the air bubbles later due to the glue giving off gases with heat increase after I brought them into the house.

Some day I hope to have a proper work space for all this and won't be working in the cold Canadian winter(although this year it's very mild)

regards
craig.