There isn't any specific documentation for MFA in SmartConsole in releases prior to R81.20.
The reason is that you would have to connect your desired MFA source to RADIUS/TACACS.
Using RADIUS/TACACS to authenticate SmartConsole users is well documented.
Note that you will only get a single password prompt.
Remote Access is somewhat different in that we added support for SAML Authentication in the JHFs for R80.40/R81/R81.10.
SAML Authentication for SmartConsole (where MFA is supported) was only added in R81.20.
Note that only your management needs to be in R81.20 to leverage this feature.