Mainlining is a technique developed by a guy called NugBuckets and was originally done with photos in order to have many main colas.
Auto's can be mainlined but is a technique for more experienced growers generally, XXL strains, Super auto's & Tall sativa leaning strains are best.
Something like Hubbabubbasmelloscope from mephisto should be good, Auto Extreme from dutch Passion should do ok too.