Wow, I just got and used a whetstone for the first time yesterday!

I'll tell you what I did, with the understanding that I'm less knowledgeable than others in this post, but can probably better relate to your situation.

I'd also be happy to hear feedback from others.

I bought a dual King whetstone of 1000/6000 grit for a basic German knife that lost its edge after a few months of daily use. The 6000 side is probably overkill (King is made for Japanese knifes, which do require 6000 grit. 2000-4000 would do for a German knife), but the whetstone was at the correct balance of price, apparent quality and known brand.

I mainly used these two videos as guides:

https://www.youtube.com/watch?v=TkzG4giI8To

https://www.youtube.com/watch?v=tahaaHxhbsA

Using a marker to see if I'm holding the knife at the correct angle helped, thought I mostly used it to get my bearings. I didn't bother with the whole 10, 8, 6 etc. stropping process, rather went a few times on each side, and tested it until the knife was able to cut through paper easily. Overall, I'd say it took me less than 10 passes on each side.

The main issue for me was forcing myself to hold the knife correctly and move my other hand to apply pressure at the right point (I was able to do it correctly, it just took a bit of work). I also had a hard time keeping the angle of the knife constant.

The whole process start to finish took me about half an hour, I'd say about 5-10 minutes were due to me being a noob.

When inspecting the edge, I noticed it was convex, which makes sense as the angle wasn't uniform. From what I understand, this might actually be better than a straight V edge (the most common type), so... yay for me, I guess?

After finishing the knife easily passed the paper test, and cutting through a tomato was more a matter of placing the knife on top of the tomato and sliding it back and forth, allowing the edge to drop down and slice it. The knife is at least as sharp as when it was new, if not sharper. There is one spot where I think the edge isn't as good, but I only noticed it because I was looking for issues and it isn't noticeable with regular use. Overall I'm very happy with the results.