I can only share my experiences... so... if you wont mod the server and use matchmaking menu with others and using standard dedicated server for that purpose, after matches with random occasions you will get skins and stuff, but that is completely random for me... and after i modded my vpk files, well, i did stop receiving random stuffs... also there is no "skin drop" screen in this, you are receiving those in the main menu and after a while you get new items onto your storage... That is my experience with this...
if you want you can use some csgo item editor to unlock skins if you want...