Not enough information, it depends on how long and how thick your wire is & how many C you battery is.
The question is how many amps will your application require and can your battery supply them.
Here is an online calculator you can use to answer your question.
Nothing special about this dimmer, you can probably get one locally. For this application, get the cheap one, the expensive ones just will not work. https://jacobs-online.biz/dimmer.htm
I'm not a big fan of using lipos, just not enough temperature control. I much prefer a transformer on a simple light dimmer switch. I have 3 transformers to get me in the correct range, then use the dimmer switch to dial in the temp. Jacobs has a great online store with a wide variety of nichrome wire and a great selection of transformers. A one stop shop for hot wire cutting, highly recommend. I've tried many wires, they will work if you just want to try cutting foam. Nichrome wire is far far superior to anything else I have tried. Far easier to get the temp right.
If you just want to try, use about a foot of thin steel wire and an old 5v wall wart transformer. The wire may need or be shorter or longer.