If you'd like, I don't know if you're still looking for tips, I could get my highlander team's engie (who is a total boss, won us several games by holding last with just him and his sentry) to give you some demos. He's a very experienced engie, and it'd be some good insight on someone with more than 1300 hours in the class. Just an offer. If you really want it, i'd reccomend hitting me up on steam with a friend request because i don't check the forums often enough.
this is my steam profile: http://steamcommunity.com/id/dotJ