Before coming to the United States, Nebres studied fine arts in the Philippines and worked in the Filipino comics industry for such publishers as Bulaklak Publishing, ACE Publications, and Graphic Arts Service (GASI).
Shortly after DC Comics editor Joe Orlando and publisher Carmine Infantino's 1971 visit to the Philippines to scout talent, Nebres began working for the American comics industry. His debut for DC was the story "The Exterminator" in House of Mystery #210 (Jan. 1973) followed by "The Witch Doctor's Magic Cloak" in House of Secrets #112 (Oct. 1973).
From 1973–1977, Nebres was a part of fellow Filipino cartoonist Tony DeZuniga's studio and emigrated to the United States in 1975.
Nebres' first Marvel Comics credit was a text article in Savage Tales #6 (Sept. 1974) and he inked the story "Dark Asylum" in Giant-Size Dracula #5 (June 1975) which was John Byrne's first work for Marvel. Nebres later drew Doctor Strange, John Carter, Warlord of Mars, Marvel Super Special, and Power Man and Iron Fist and contributed to Marvel's black-and-white magazine line, Curtis Magazines, most notably on Deadly Hands of Kung Fu.
From 1980–1983, he drew stories for Warren Publishing's Creepy, Eerie, Vampirella, and 1984 titles. Following his stint at Warren, Nebres worked for Pacific Comics, Archie Comics' short-lived superhero line, and Continuity Comics.