it IS one of the hardest things to get to grips with in this game, and if you rely on bearing plots to obtain your solution it becomes an even bigger problem, as errors in range lead to errors in target course and speed.
There are a few things you can do to improve your chances.
Firstly, focus on other methods of getting target course, inlcuding your ability to judge AOB by eye. AOB + poor range estimate is more accurate than two poor range estimates. Also try using the aspect ratio method of getting a good AOB
Secondly, focus on obtaining speed estimates by other methods than bearing plots. Errors in range with this method also lead to large errors in speed estimate. Using the slide rule on a whiz wheel is one way to find target speed, which in short means you try to set up a collision course with the target typically on your beam (ie bearing 90/270 from you). Also you can get speed estimates by observing the time it takes for the ship to cross a fixed point, e.g. your periscope cross hairs. you have to be moving slow, but then you can divide the length of target by time to get speed in m/s. double this to get speed in knots.
Thirdly, if you really want to get a bearing plot, plan on getting a large number of bearings plots in order to even out inaccuracies
Fourthly, focus on closing the gap until the range is close enough that errors become less signiricant, fro example by holding the target on a normal approach course of 90/270 degrees.
Fifthly, if the weather is very rough it can be easier to just count the marks on the periscope and do the maths yourself to find an approximate range (also to be done if you have to use your obs scope for targeting)
With all these methods working together, poor weather is just a little challenge. If you are playing GWX you find the disadvantage of rough weather is much more than compensated for by the bad effect it has on your enemies sonar
