I've been a supervising manager in several environments, and what I'm suggesting has worked for me when I had the following:
A) Fill out the forms for your team just one month after the last review with the "current state" of progress against the goals. The first month it takes awhile to fill in all the information, But it's all typing since there probably isn't much to report yet against full-year goals.
B) Every month, schedule some time to update all those reviews. As you will just be making incremental changes to what you already have based on only one mont's progress. And, you have all those emails and one-on-one forms from the month to refer to so this won't take long at all to do and do right. Doing this for a staff of 5 rarely took me more than one hour a month. Do it at a regulalry scheduled time you can block out in advance (i.e. 2:00 pm on the third Friday of each month).
When the end of the year comes and every other manager is sweating bullets to get their reviews done, you not only take just an hour or two to add your latest month's updates and put the finishing touches on the document, but then you get all that free time while your peers are doing their team's reviews to go do some of your pet project work while they are busy doing other things and NOT asking for your time. It's like a little vacation at work.
One hint: DO NOT get cocky and turn your reviews in to HR (or your boss, as the case may be) the day after you get the forms. No matter how much back-up you have and how many times you explain your system to them, they will insist you slapped something together in a hurry and will send it all back to you to do again. Sit on them for a few days, then send them in. If nothing else, it gives you a change to reflect to make sure your reviews are as well written as you would hope.