The point of this essay is not in depth detailed knowledge, it's about deploying knowledge to a question with tact and skill, and to only illustrate the point you're trying to make and to highlight similarities and differences. For example, if you're talking about the way regimes were oppressive, you can use the ways Alexander II and Khrushchev dealt with the hungarian riots of 1861 and 1955 respectfully. The point of the knowledge for a high-end answer is to facilitate the comparison between different leaders.
Another way to get an A or A* is to have good synthesis between your paragraphs, think of good ways to link together key themes, i.e the economy affected the political climate and this in term affected the social aspects of russia is normally my preferred way of structuring the themes, but within that your last and first example should have some linkage, sounds slightly trivial but it really helps with a flowing essay and shows the examiner you've thought clearly and precisely and deployed your knowledge selectively rather than put everything you know on the page.
a plan for some people helps for others it doesn't, if you feel confident enough with your ability to plan as you go along it's worth saving the five or so minutes. I prefer not to make an overt plan and save the time, instead using my introduction as a plan as that's essentially what it's there for. besides this, it's all down to your technique, sounds boring and oldschool, but do plans practice writing in timed conditions, get your technique nailed.
What I did for my preparation is look at the past papers see what HASNOT come up, and try focus your plans on this. again look what are less common questions and aim your focus towards this as well, after all if a question have been asked on the past 3 exams it's unlikely to appear. again with this exam there are only 4 areas os study they expect you to know, so knowing things about the economy of Russia and key facts which will really help your argument. Nature of Government is also a key so knowing facts about the structure of the duma or the prov. govt. aren't going to hinder you.
As revision goes, attempt to look at an event then split it down into how it affected society politics and the economy. then when you get a question, you're going to be more able to deploy examples, especially when you're trying to include leaders which you think made little impact but need to get them in for full synthesis,
hoped this helped,
Tom