Every week I wash my hair I style it into bantu knots to stay in until the next wash day. Like this week I dusted my ends. So since I do everything in small sections (wash, detangle & style) I just twisted each piece & then lightly dusted each end before I made each bantu knot. Very simple & effective.
I don't believe you really need to trim your hair unless you want to, you're in a rush to get rid of the relaxed ends or they are very damaged (well I can't even say that. My hair was badly damaged when I started & I never did a dust or trim until 4months in & there were no major issues). However I would not necessarily recommend doing the same to others.
Some people swear by cutting straight, others wet & curly. You will just have to experiment & see what works best for you and your hair. However I would really suggest only dusting if your apprensive about cutting your own hair. When you dust you cut soooo little off anyway it really won't effect your length anyway.