I'm assuming you are wanting to bottle in Belgian bottles (750 ml with the fat, roundish lip on top). It is not possible to "cork by hand" using standard belgian corks. some people report success using plastic champagne corks (using a rubber mallet and gently tapping them in). to do real corks, you really need a corker to compress the corks evenly and push them partially into the bottles. There are a few threads on corking Belgian bottles...use the search function on this forum to find them.
Lots of Homebrew stores will rent corkers for something like $10/day...these are usually wine corkers, but will work for Belgian bottles...the trick is to only push the cork part-way into the bottles (leaving enough to afix the cages). I've heard people having success putting a stopper over the plunger (I don't recall which #) preventing you from pushing the corks too far in.
Personally, I just invested in a Colonna capper/corker (~$65 as opposed to $150 for an actual champagne corker)...works great for capping standard 12 oz bottles and 750 ml bottles (with the larger caps) as well as corking...it is not really made to do Belgian bottles, but it works (again, use the search function to find exact instructions)