Remus knew he was blushing. His cheeks were very warm, and though he couldn't see it he knew his cheeks were pink. Sirius always managed to cause that reaction in him, whether he knew it or not. There was an undeniable smile on his lips as well, as he watched the other boy react to his words. He looked happy, which made Remus happy. That was what he wanted more than anything else, for Sirius to be happy.
"Years of practice," he retorted in a light tease. In truth, he never thought it possible for Sirius to love him back either. It just didn't seem likely at all to happen. SIrius could have anyone he wanted; why should he want him?
To address the fears Sirius expressed, Remus leaned in to press their foreheads together. "I'm sure there will be plenty of time for all that, when you're ready. In case you didn't know, I'm terribly patient."