The reason I'm thinning the tru oil is because it gets tacky really fast which result in a lot of stroke marks and dust specks that sticks to it, do you think I should go with pure tru oil anyway? I'm afraid that I won't be able to remove all the defects if it will get too thick.
I can only go by my own experience of not thinning. If you're working in a particularly dusty environment, maybe what works for me won't for you. My workshop is a metal shed (1-car garage sized) and far from dust free and I work with the overhead door open most of the time. I do have and use a portable spray booth (tent - but larger than Simon's) but only if I'm spraying lacquer.
Any hand applied finishes, I just do on my bench.

Sounds like you've already tried it undiluted, and it didn't work for you.