EDIT: my bad!! I just realised you were only looking for ways to put the pins back in. Anyway, I decided to leave the whole thing here so people who make a search will also find this post and maybe find it useful.
Go to the end for putting the pins back in.
Either you have the tools or you don't. I don't, so here's how I do it and things you shouldn't do from my own experience. This is the cheapest way of doing things, believe me.
1. get tweezers
2. get a plug follower (I found a permanent marker pen that fits just right, but I also use.... drum rolls.... ...... a ripped in half and rolled up beer mat from a pub - this actually works very well as the rolled up part make it fit many plug sizes!! - one of those round ones, not square ones)
3.

when you remove a pin, make sure you remove everything!! That includes the bottom pin, top pin AND the spring. Failling to do that will result in disaster when you put the plug back in. Experience, experience.
4. insert key in lock. Turn the key slightly to 1-2 o'clock. Place the plug follower at the back of the lock and use it to PUSH the plug out. It will feel like magic when it works out right and nothing savagely jumps out of the lock.
5. remove pins one by one. This will prevent things from flying everywhere. Start at the 'back' of the cylinder.
6. Leave the first 2 or 3 sets of pins as to your liking. Now you should be in this position: the plug follower is protruding from the front of the lock and extends to the 2nd or 3rd set of pins (depending on how many you left).
7. put the plug back in through the front and make it push the plug follower all the way out. When you do this, make sure the plug is turned to a little angle again (1-2 o'clock) so that the pins don't fall into the holes if by mistake you forgot to leave the key in the plug.
There. Hopefully it worked.
-- putting pins back in:
Push the plug out with the plug follower. Then push the plug follower in until it covers the pins but leave it just behind the hole you're going to fill.
You will have to put in the spring first. That's easy. Some springs are quite tall and hard and might be more difficult than others for what follows.
Then try and force the top pin on top of the spring into the hole. While you do this, slightly push with the plug follower to bind the top pin in place.
Once you have donw that, ungrip the top pin (it should stay in place half sticking out, being 'binded' by the plug follower).
Use the tweezers to push the top pin into the hole, while pushing forward gently with the plug follower until the top pin moves entirely into the hole and it is covered by the plug follower. SUCCESS!!
Now do the next ones.
Have fun with it all, that's the most important. If you can't replace pins with a rolled up beer mat as a plug follower then I suggest you buy really expensive equipment
L.