There’s a handy function in iOS that’s easy to miss. You can swipe across the screen to select more than one photo at a time, which is a huge speed boost if you ever need to trash a whole bunch of pictures at once.
First, tap Select in the top right of the Photos app. In addition to tapping to choose individual pictures, you can press and drag to select multiple photos at once. Once selected, you can share, delete, or add to an album as you would with a single picture.
Bear in mind that it’s easier to start the selection with a sideways swipe, as swiping up or down usually results in scrolling through the stream rather than selecting images.