The valve anti-cheat system is designed for co-op and multiplayer games only,
You can not be (vac banned) for playing single-player games by yourself.
However, if you started a co-op and multiplayer game or maybe joined one, then started to use that trainer on a "Vac" protected server, nothing is going to save your bacon at this point, so just make sure to always choose the option "Play offline - single player" so you are not going to have to connect to any of there servers or networks whatsoever. Normally "Vac" protected games have an option to turn this on and off, like dead island and resident evil 6 and some other games,
You will be fine, just do what your already doing, "Play offline - single player"