If I understand it correctly, you are dealing with three sets of genes there...
F/f Frizzle, H/h Silkie, and the mf/Mf? Frizzle Suppressor gene
Frizzle Feathers... F for Frizzle type, f for the normal type... Frizzle is an incomplete dominant, so 1 copy gives you a Frizzle bird (Ff) and two copies gives you an even more frizzled bird that people seem to call a Frazzle (FF) and ff for the normal feathers. The Frazzles have really poor feathering so most people want to avoid them.
Silkie Feathers, h for silkie, H for normal type, Silkie is a simple recessive (need two copies of the gene to be expressed)... Hh or HH gives you normal (Hooked) feathers, and hh for the recessive hookless Silkie feathers
The big question mark with crosses seems to be the Frizzle Feather suppressor gene - Mf/mf ... when you have two copies mf/mf of this it suppresses the expression of the Frizzle gene(s) in Ff birds so they can look physically a lot like an ff ... so the Frizzle is somewhat to almost completely hidden. But it in FF birds (according to the one paper) it only expresses about 40% of the time, so most still look like Frazzles but some will look like Frizzles, some other papers give different numbers. The mf/mf recessive is in most birds that are not bred / selected for Frizzle. Birds that have been bred for Frizzle and selected for expression like the show type ones will most likely carry Mf so the Frizzle is expressed correctly.....I think is what they are getting at.
So if you breed a Frizzle Ff to a Normal ff you will get 50/50 Ff and ff birds... but what the Ff ones look like will depend if the Frizzle parent was MfMf or Mfmf since the Normal will most probably be mfmf unless you are using a Normal from a Frizzle breeding program ...
If you breed a Frizzle Ff HH to a Silkie ff hh you would get 50/50 Ff Hf and ff Hh birds ... so half would be Frizzles, and half would be Normal feathered, but they would both carry the Silkie gene but not express it since they only have one copy...again how the Frizzle would express would depend on the mf gene..
If you breed your Ff Hh bird back to a Silkie ff hh you would get a Ff Hh, Ffhh, ff Hh, ff hh ... so you should get 25% Frizzled Silkied birds (what they actually looked like depending on mf again)
If you breed the Frizzled Silkie (Sizzle?) Ff hh, to a regular silkie ff hh you should get 50/50 Sizzles Ff hh and Silkies ff hh ... Frizzle again depending on the mf ...