I do both.
Sometimes I will start up top and work my way down and other times I will go deep and work up. I mainly do whatever it takes to get bit.
As far as deepest depth...I have caught fish in the Summer in 35 feet of water right on the bottom. I have also caught them in as shallow as 6 feet of water early in the day.
When fishing timber simply start out at a depth and start going until you get a bite. After a few trees and strikes you will zero in on where they are hanging out at that day.
We fished a tree in 36 feet of water a couple weeks ago.
We started at rod length or 8 feet and nothing.
We went to 10 feet and nothing.
We went to 12 feet and nothing.
We went to 14 feet and nothing.
We went to 16 feet and nothing.
We went to 18 feet and SLAM! Dropped down to 18 feet again and SLAM! Dropped down to 18 feet again and SLAM! Dropped down to 18 feet again and nothing.
We dropped down to 20 feet and SLAM! SLAM! SLAM! SLAM! then nothing.
We dropped down to 22 feet and SLAM! SLAM! SLAM! SLAM! SLAM! SLAM! then nothing.
We dropped down to 24 feet and nothing.
We dropped down to 26 feet and nothing.
We dropped down to 28 feet and SLAM! SLAM! SLAM! SLAM! SLAM!(SMALL ONES)
We dropped down to 30 feet and SLAM! SLAM! SLAM! SLAM! SLAM! SLAM! (SMALL ONES)
We dropped down to 32 feet and nothing.
We dropped down to 34 feet and SLAM! SLAM! SLAM! (BIG ONES).
Then nothing.
27 fish off one tree with 16 keepers. All we did was fish until we got bit and we would zero in on that depth until no more bites and then keep varying the depth. If one is there they will hammer it. If not go find a tree with one that wants to hammer it. I am sure there are a ton of techniques...just sharing what I do.
You can also drop down to bottom and then wind a crank and wait and then wind a crank and wait and see if you get bit on the way up.
Good Luck. If you have any other questions feel free to ask.