These look neat, but is there any practical way to enter them quickly while coding?
What do you mean? The whole point of ligatures is that you don't enter them, they're not specific code points in text, they're just different glyphs for specific combinations of characters in text (otherwise you're code would be turned invalid). A glyph for "=>" is just the programmer's equivalent to an old-fashioned glyph like what you often get for "fi".