One of the describe/compare/contrast 3-styles questions I had was the 3 beers in Category 8. Best Bitter, Special Bitter, ESB.
It's the last question I've got left to answer, and I'm running out of time.
First of all, you should have had a blank grid made up before the exam started. The "compare 3 styles" question will always be on the exam in its current form.
Second, prioritize and condense information. For example, don't mess around with mentioning that you can actually have American or Continental hops in an Ordinary Bitter, instead say something like "Herbal, earthy English hop notes typical." Only add the additional info if you have time. When possible, summarize sensory descriptors, e.g., "dark/dried fruit esters" instead of "dried cherry, fig, date, prune or plum-like esters." Abbreviate and use bullet points when possible.
Third, practice describing beers in a set fashion so you can work more quickly. For example, I always describe base malt first, then specialty malt, then hops (bittering, flavor, aroma), then yeast character, then oddities and style specific flaws (e.g., coriander, curacao orange, chamomile and slight lactic sour in a Belgian Wit. No ham-like or soapy notes.)
Fourth, get in the habit of describing location, intensity and character of each element. For example, don't just say "English pale malt." Instead, write something like "Initial moderate bready, sweetish pale malt notes" or "Subtle, lingering, pleasant hop bitterness in finish."
Fifth, and this might have cost me this last time around, for many styles aroma and flavor are basically identical. In those cases, you can MAYBE get away with writing something like this for flavor: "Malt and late hop character "follow the nose" and are similar in profile to aroma description." Then you go in an describe flavor specific elements like hop bitterness, balance, finish and other elements which aren't addressed in the aroma description.
Perhaps, maybe, when describing two very similar styles, you could write something like "Similar to X, but more/less malt/hop/yeast character, higher/lower alcohol character.
When two or more styles are identical, as in the compare and contrast sections, I think it's safe to draw arrows between like styles or have comments which straddle two or more columns (as long as you can do so legibly). If not, make your compare and contrast notes obvious. E.g., "Same base malt, hop varieties & yeast strains for all sub-styles" or Ordinary Bitter & Best Bitter: Lower in alcohol, often lighter in color & less hop aroma and flavor than ESB."