If you're going to try and block him I suggest learning his/her online times. takes some time but done right you can figure out the ideal time.  For the units to use  thats something you have to figure out. Each unit type has units its good against and those it can't attack or defend well against.  Like a dagger is a horrible unit to use for offense. 

The best units though to use for a block you should aim for 4-5million defense in subs at least. Remember it only takes a bit more than 50% to break the block.  I

If he's freed, I wouldn't suggest reblocking him unless you know you can hold a second block and get thru his def at the sametime.  

Now if you want to annoy him - here's a couple suggestions

 1. spam scout or raid him = send a single unit per raid/scout/block but you're doing this 40+. Do this a few times and you can actually use this as a way to catch him off guard by sending a real block in the middle of it all. if you do that make sure it doesn't go faster than the fakes. It'll be obvious if he's watching for a trojan horse. 

2. Make it so none of his friends can send him resources. Max res transfers a person can receive is 6 I believe.(someone else can correct me if I'm wrong) Either way you get your friends to help you with this one and send a single unit of rum each. Do this for a few days or even a week, you'll definitely get under his skin. When you can't receive resources everyday for X amount of time because an enemy decided to spam you. Its going to flip your lid. But this is also where he/she may make mistakes.

Good luck 

Hit him with fireships until he has no troops left...then send a blockade.

fireship route is possible but not completely probable.  In some cases you'll need 100+ to be successful going this route.  1 fireship does 12500 damage. You have any haven guards and walls adding haven defense plus any defense left out. Also the max per strike is 10 fireships at a time with a max per reset of 10 strikes for a grand total of 100 fireships. At 500 rubies a pop you'll spend 50k rubies. Each strike will only do 125,000  if sending the max of 10 fireships for a grand total using all 100 of 1.25 million. If they have 10 million in defense sitting out which is not unheard of the fireship route is a waste of rubies.

Now blockading isn't the only thing to consider you also need to be able to hold the blockade. So you need to have an adequate defense their. Remember it only takes 50% to defeat troops so arguement sake you have a 3million defense parked then the other player or any of his friends only need 1.5 million to break your blockade.

Walls do nothing against Fireships.

Buying Fireships at 500 rubies apiece is wasteful. Wait for a global discount.

Speaking of its been awhile can we get a global discount