Route guest Wi-Fi traffic through second ISP

Hi! I have simple failover setup with two ISP’s, just two static routes with “ping” option.
Can I use my second backup ISP for guest wireless network and how?

Use Mangel to Mark Routing, specify the sr-add of Wifi customers;
set up routing rule to catch that routing mark, specify its gateway to be your 2nd ISP
create NAT rule to masquerade, specifi WiFi users IP address range and out-interface to be your 2nd ISP.

Thank you, it works.