Don’t go to instruction books. Go to the best Muscle Bear comics in existence today: Bakudan Comics from Japan. Get ’em @ g-men.co.jp. You want to study the styles of artists like Gengoroh Tagame, Jiraiya and Seizoh Ebisubashi. Spain’s Ediciones La Cupula has published some of Jiraiya’s great artwork in Spanish-language versions. Also try to get hold of one or more of the three volumes of Gay Erotic Art in Japan. They’re often available on eBay; pricey but worth it. You also want to study online samples of hard-to-get Gay Manga artwork by Go Hirano and Sadao Hasegawa. Finally, make sure MASSIVE by Chip Kidd and Anne Ishii is on your bookshelf. It’s an indispensable anthology of Gay Erotic Manga. Nobody does Muscle Bears better than the Japanese graphic novelists.