We can send btc, right? From stock exchanges?
You should not send BTC/ETH from an exchange or you risk loosing your coins. You should hold the private keys to the wallets you use for crowdsale.
You can take part with BTC for the first 24 hours. 1 BTC = 6000 RLC
You can take part with ETH through the whole crowdsale. Price of ETH/RLC will be adjusted every 10 mins according to Kraken price
Hope this helps
Why only Kraken? Largest ETH exchange is poloniex, you should use a average price or poloniex instead of Kraken's price.