not easy

for hedgehog to work you have to create a preimage & hash in every transaction, as well as two bitcoin signatures. A guy in this video shows how to create a preimage & hash with pen and paper. It looks like it would take about 8 hours of full time work and you'd probably make a mistake somewhere, so you'd likely need a team of three people to check your work. It is my understanding that creating a signature manually is about twice as difficult as creating a hash manually, and you need two of those per transaction so it's about four times as much work to make the signatures. So you're looking at five days of 8 hours of work for a team of four people -- per transaction.

But why do this with pen and paper? In this hypothetical scenario, did the USA also confiscate and ban all graphing calculators? It only takes a graphing calculator about a second to calculate a hash or a signature, so you'd simply have to program it for that -- and I'm sure such programs would be released as shareware. (There's one for gameboy already, so start with that and modify it for a ti-86, which should be easy because they are both 8bit processors with Assembly support. Or literally use a gameboy.)