Bin is fine but you should still rub it down to get rid of the nibs and bits that may be there now, especially being a shirting which does tend to gather more muck in the paint for various reasons.
The paint..plus have pluses and minuses...it deepends what you are looking for and what you are happy to sacrifice..
Water based advantages, quick drying, stays white, very low odour, easy to clean brushes and rollers..fairly hard wearing
Disadvantages...the quick drying bit might also be a pain when doing a large area of anything fiddly as the edge will go off quick before you have a chance to lay the paint off...doesnt adhere to most traditional painted surfaces...slighty different techniques are required when applying it..lots of painters I know say it feels like your glossing with vinyl silk emulsion. (id recommend a synthetic fillament brush not a traditional type)
Oil based...advantages can be used over most other types of coating, not to much practice required putting it on, hard wearing finish.
Disadvantages...strong odour, will go yellow over time, might run, clean up using white spirit or turps substitute.
Finish wise there isnt too much of a differenct..although some water based eggshell can have a bit more of a sheen to it than oil based.