For the OP question: yes, there are starter cultures you can buy. It should start on its own if you have a good mix of green/brown, add some garden soil that has some worms in it will help.
I have used three different methods.
My first life, in NE PA, I nailed three wooden pallets in a U shape, put it off to the side of the yard. Yard waste, kitchen scraps.. Everything went into it. Yeah, raccoons would visit and paw through it at times. I would just shovel what they spilled out back into it.
Convenience – Excellent. Just take whatever you had a dump it on the pile.
Success for useful product – None. I think I just never generated enough to make it work. I was single so minimal kitchen scraps and really did not rake or bag grass clippings or leaves, so very little actually went in. It really broke down to nothing. Lol!
In Nawth Kackalacky I had a 50 x 100’ garden. I dug a trench where I would plant a row of something the next year: a shovel wide and maybe a shovel deep. Over the course of a year I would just dump stuff into it and push some dirt on top as I went. Not filling it with stuff, but… kind of spread out as I went. I guess it was always a few inches deep after green stuff wilted and coffee grounds, apple cores and all. It might be a pile that filled it, but it would settle down to a couple inches kind of thing.
Convenience – Excellent. There was always a place to just dump and run. You could come back later to fill if you were in a hurry or just did not feel like it.
Success – Great as far as I could tell. By planting time all except the newer parts were all but discernible from black soil. Within one year, you might see some pieces of orange peel, or chicken bones or something like that. I would move it to the next row as that one filled and just not plant there that year.
I am suburbia now and we have one of the rotating barrels. Just put kitchen scraps in it and give it a turn or two after I dump in.
Convenience – Excellent – at first. Open, dump and run. Later… It needs to be dickered with to work. It can dry out, so needs to be watered. It can get too wet so needs something to help dry it a bit. Over the winter here in Delaware, nothing composts down, it just freezes. You need to get a good mix of colors too, greens/browns, to make it work effectively. It can get smelly if it is not working fast enough, stuff rots more than composts. It takes some looking at to see what it needs, usually green, water and some worms. Give it a turn or two and a few days later it is working again.
Success – Excellent, but a PITA! Just make sure you get one to where a wheelbarrow will fit under it so you can slide a wheel barrow under it, open the hatch, turn the barrel and let stuff fall out into the wheel barrow. The one we have is too low AND narrow to fit a standard Jackson M5!! Bastages. You can’t really be accurate enough to put a 5-gallon pail under it to fill. I have a large piece of black plastic. Spread it out, dump (yeah, you need to get a shovel in there to help unload it too). The end product is very nice if you paid attention.