Body inflation

Help/advice with realistic neck inflation, no skin showing.

Hello,
I'm kind of new to this so I'm not yet sure if I need inflation or padding help but I decided to go with inflation as a start since I'm planning to do that for my belly also.
I'm not too chubby myself but how can I have a realistic looking thick fatty neck shape (covered by clothing entirely, no skin revealed). Everything I've found online so far has been about belly or boobs inflation, the only material I've found about neck is some silicon prosthetic that you're supposed to makeup to look like real skin and I don't have that kind of a budget anyway, I'm only starting out.
How do I cheaply DIY a fat neck so my belly doesn't look completely out of place. I'd like to think using water is the best avenue but I'm open to padding as well for the neck.
I want to cover my entire head and neck and well my entire body really with fabric and clothing anyway so it just needs to have a somewhat realistic shape and weight to it.
The thing that is the hardest is how to connect it naturally to my real head shape such that it doesn't look like I'm wearing a thick gaiter of some kind.
Please be nice I'm very new to this forum and hobby.
2 weeks