Mixing Dash is actually very simple.
1) Sell Dash for XMR on Poloniex
2) Send XMR to own XMR address
3) Send XMR to a second XMR address with a mixin of say 5
4) Sell XMR for Dash on Shapeshift.io
Voila! Mixed Dash. No need to wait for weeks or worry about masternode blinding.
Edit: When sending the XMR to Shapeshift.io also use a mixin of say 5
What does "mixin" mean with XMR? Does Monero also use mixers to mix coins?
mixin - the amount of outputs taken from the block chain to mix with your outputs in your wallet.
So if you have the following outputs and want to send 431XMR:
1XMR
30XMR
400XMR
with a mixin of 5....
you will get 5 - 1 xmr outputs
5 - 30 xmr ouputs
5 - 400xmr outputs
to mix with.
Outputs are broken down into powers of 10 so there is a mixable set on the block chain.
There is more to the privacy when you read the monero lab papers. The math backs the claims of using mixins at different levels.
Probably not the best explanation but that's my understanding of how it works based on reviewing the code.
Mixing can be done completely offline (generating the transaction) and you do not need other parties to mix with like with Dash/Coinjoin etc.