Tuga was four months old when she first killed a toy mouse. Properly killed it — stalked it across the lawn, got the back feet right, landed the pounce, and then carried the corpse around for an hour looking insufferable.

The mouse was pink and made of felt and had never been alive. That did not make the practice less real. Every component of the hunt was rehearsed on something that couldn't bite back, couldn't escape, and cost nothing if she got it wrong.

Bitcoin has a pink felt mouse, and almost nobody uses it.

1. There Is a Free Copy of the Whole System

Testnet and signet are parallel Bitcoin networks that work exactly like the real one — same software, same addresses, same transactions, same fees, same wallets — with coins that are worth nothing and are given away for free.

You can get a pile of them from a faucet in about thirty seconds. Then you can do every single thing I've described across this entire series, with zero consequences for getting it wrong.

Signet is the better one for practising: it's more stable than testnet, blocks arrive reliably, and some variants produce them far faster than every ten minutes, so you aren't waiting around to see a confirmation.

2. What Is Actually Worth Rehearsing

Not "sending a transaction" — you'll manage that. The things worth practising are the ones you'd otherwise do for the first time under pressure, with real money, possibly at 2am:

• The wipe-and-restore drill. Set up a wallet, fund it, wipe it, bring it back from the words alone. Do it until it's boring. This is the single most valuable rehearsal there is.
• Assembling a multisig. Create a 2-of-3, fund it, sign with two keys, and — crucially — destroy the setup and rebuild it from the descriptor and seeds alone. If you've read the descriptor article and felt a small cold feeling, this is how you resolve it, for free, this week.
• The air-gapped flow. Build a PSBT on one machine, carry it by QR or SD card, sign it, bring it back, broadcast. The workflow has rough edges and you want to find them now.
• Fee bumping. Deliberately send something with a stupidly low fee, watch it sit there, then rescue it with RBF. Then do the CPFP version from the receiving side. Ten minutes, and you'll never panic about a stuck transaction again.
• Sweeping an old key. Generate a key, send to it, sweep it to a fresh wallet. Exactly the procedure from the forgotten-wallet article, with nothing at stake.
• Lightning. Open a channel, send, receive, close it. Discover inbound liquidity as a concept rather than as an obstacle on a day you needed to get paid.

3. How to Get Started

• Sparrow has a signet/testnet mode in its settings — it's the best desktop environment for practising coin control, PSBTs and multisig.
• Hardware wallets generally have a testnet setting or a separate app you have to enable deliberately. Worth knowing where that switch is anyway.
• Faucets hand out coins for free; search for a current one, because they come and go.
• Mutinynet is a signet variant with fast blocks, which makes Lightning practice bearable instead of glacial.

Half an hour of setup, then an afternoon of breaking things on purpose.

4. The Honest Limits

This is practice, not a substitute, and the gaps matter:

• You don't learn the fear. Signet coins are worthless, so your hands don't shake. The one thing you cannot rehearse is what it feels like to send real money to a new address for the first time — so after the practice, do a real transaction with a trivial amount. The fear is part of the procedure.
• You can form sloppy habits. It genuinely doesn't matter if you lose signet coins, which means it's easy to skip the careful step. Practise as though it counted, or you're rehearsing the wrong behaviour.
• Mainnet fee conditions are different. Signet never gets congested the way the real network does. You can learn the mechanics of fee bumping, not the judgement of fee markets.
• Don't mix them up. Keep testnet wallets clearly labelled and separate. Confusing a practice wallet with a real one is a small embarrassment on signet and a disaster in the other direction.

5. Who Should Do This

Anyone about to do something they haven't done before, which is most people reading this.

If you're setting up multisig, rehearse it on signet first — the rebuild-from-descriptor step alone justifies the afternoon. If you're about to buy a hardware wallet, practise the restore flow with a software wallet in testnet mode while you wait for delivery. If you've been meaning to understand coin control or PSBTs for a year and keep not starting because the stakes feel high: the stakes are zero and have always been zero.

The Point

The pink mouse was never going to feed anyone. What it did was let a four-month-old cat get every part of the sequence wrong, repeatedly, in a garden, with no cost beyond her dignity — so that when something real moved in the grass, the movement was already in her legs.

You can have that. The entire system, free, with the same software and the same mistakes available. The only reason more people don't use it is that nobody tells them it's there.

Learn it on the toy mouse. Then go outside. 🐾⚡