Best Engineer Monkey Path
If you are running top path with it i would highly suggest. The sentry gun isn’t very good by itself, but with other towers. Webmiddle path is very useful if you know how to use it and it's definitely my favourite but if you want just put tower down and win than to path is my recommendation. Probably middle path big damage: Towers have special roles to play for.
Top path farming and catching leaks: Webtop path engineer is a’lot of things, mostly popping power, but lets start with the basic upgrades. The first upgrade is larger service area, it gives the engineer monkey the crucial extra range he needs.