Best way to Micro/split push with Phantom Lancer

Select the units you want to send down the lane, assign them to a control group by pressing control + 1-9 (optional), and press A followed by a left click. They will attack anything along the way to where you clicked.

Learn to use Dota 2's console, and type dota_player_multipler_orders 1. All you need to do now is to create an army of your summons, hold down Ctrl, press A (Attack) and left click into their base. Then all of your units will attack towards that direction, and you simply recontrol the command of your hero.

This way you never have to worry about grouping your temporary summons, and it's handy to not loosing focus of your hero.