You'll want a paper trimmer to trim print to final mount size once the tissue is tacked to the back of the print. I use a cheap iron bought from a hobby shop. I buy tissue in rolls to have any size available I need. Like Wildbill I use parchment paper from the local grocery store for a release paper and put mount under a 2 ply Matt board while in the press. If I have many prints to mount at a time I take each print out of hot press and put between two sheets of 1/4 inch plate glass (it's the flattest stuff I have, other flat surface should work fine) with a 20 lb barbell on it. If I'm only doing a single print, I'll just turn the press off and let the mount cool in the press which always give flawless mounts with no edge lifting which can sometimes happen. In our climate I don't find it necessary to pre dry the mounts unless you have bought the Matt board recently from a source that has a humid climate and it is still sealed up in plastic not allowing it to dry out.
I find it easier to tack the print to the mount board by eye. Just line up the over Matt on the mount and stick the print where it needs to be and tack it down. Much less time than measuring out lines and such. I don't mind cutting my own over matts, it's pretty simple once you do it a few times but if all your prints are uniform in size a pre cut overmatt makes sense because you don't really save much except you can often use the cut out from the overmatt to use a mounts for smaller prints when you do it yourself.
I'm sure after you do the whole mounting thing, you'll pick it up pretty quickly - it really is simple. Here's a pic of the parchment and tack iron I use if it might be useful.