How to paint textured wall corners? all my walls are textured... i would resembling to use a different...

all my walls are textured... i would resembling to use a different color on one wall but the corner is really textured, i couldn't draw a straight line not evan next to a ruler. please help me to find a solution!
THANKS
How can I prevent my hand from getting...
Answers:    I would try using some blue cartridge and tape stale a line as staight as you can down the corner. If that doesnt work try 5 contained by 1 (scraper) painters tool and drag it down the corner a few times to win you a nice line to step by.
Breaker blowing when power is turned stale?
Just tape as close to the corner as you can. Make sure cassette is down good. When you start to paint keep the brush only on the one wall even though other wall is taped, because on really texture walls you won't discern how close your edge is but if you hit the other wall....not well brought-up. Ok. Get a good brush too, I similar to angled.//////