The problem with Remus' theory was that in order to get dressed, Sirius had to get undressed first. His second problem was that he had placed himself upon their bed. A deadly combination. Especially once Sirius had quickly stripped, tossing his clothes helter skelter about the room.
Buck naked, he turned with glee to his mate, and pounced upon the bed, pulling Remus down on him, his lips capturing that of the wolf.
With his mouth occupied, Sirius could hardly utter a word. Good thing he knew wordless spells. He used the one for making Remus naked and was well pleased with the results, as he began to rub their bodies frantically together.