Well...i don't exactly just have one block, although I've seen many who do. I have the advantage that I mounted a tall arch on the back of my boat - the top of it is about 4' above the rear deck. I got the idea i used fron others who had a factory rear railing, like on the 26M boats.
So my uphaul line starts by the tiller post, attached to the transom. It goes down to the back of the rudder where it passes thru a block that is lashed to the back of the rudder...the lashing is loose enough that that block stays just high enough to stay pretty much out of the water when all is at rest. The line turns upward and goes all the way up to the arch. There is a block lashed up there that the line passes thru then aims down at the deck again. I tied a spring clip to the end of the line there. When i want to raise the rudder all the way up, i just grab the clip (it's a pretty good size one so it works like a handle) and pull down toward the deck. (One advantage is that i am pulling down, so i can sit in the cockpit and do it pretty comfortably.) I clip it to the leftover mast crutch tube holder and it stays up very nicely and securely. When i want to lower the rudder, i just unclip it and let go. The weight of the rudder pulls the rope thru and the clip rises up to the arch. (Then I pull on the downhaul to finish and secure it.) I had to work with the lengths a little to get it right, but it seems to work pretty well so far.
You can definitely work out a multi-part arrangement to get a better advantage. But if you don't have a railing or arch or something up above the transom, then you'll have to locate something to hang the blocks from...maybe even adding a small bracket to the back of the transom.