Picnic was never one of my favorite Bill Holden films, he was too old at 37 to play the love interest of a 22-year old Kim Novak-- BUT that was the way of Hollywood at the time.
There are so many good films of his such as Rachel and the Stranger, Sunset Boulevard, Union Station, Force of Arms, Stalag 17, Executive Suite, The Bridges at Toko-Ri, Sabrina, Love Is a Many-Splendored Thing, Toward the Unknown, The Bridge on the River Kwai, The Horse Soldiers, The World of Suzie Wong, Satan Never Sleeps, The Counterfeit Traitor, Alvarez Kelly, The Devil's Brigade, Wild Rovers, The Revengers, Network, Damien: Omen II and my favorites The Wild Bunch and Blake Edwards' S.O.B.
If you want to see him actually drinking while acting, watch Paris When It Sizzles. Bill has a brief love affair that did not end well with Audrey Hepburn when they did Sabrina together ten years before and he still carried a torch for her. He spoke about it:
"I remember the day I arrived at Orly Airport for Paris When It Sizzles. I could hear my footsteps echoing against the walls of the transit corridor, just like a condemned man walking the last mile. I realized that I had to face Audrey and I had to deal with my drinking. And I didn’t think I could handle either situation."
When ever I think of Bill so saddly dying alone too damn drunk to treat a cut on his head I always add "--but for the grace of God that could have been me--"