here my usual way off playing an engie
1. build a sentry and dispenser in your base ( usualy near spawn)
2. let a pyro be near your dispenser and sentry
3. go afk for half hour and do what you want youtube read a book,...
4. look at your sentry kills and be
if this doesn't help you out then your doing it wrong ( don't blame me D:)
this is all thank you ( btw my first post)