TFR might make the job a little faster, but it certainly isn't a vital component of your arsenal.
Well it is for me & spraying it on is the best option.
I want it, as part of my advertising will be " If i can't get it clean DONT pay me" the idea being i will clean 1 section of the conservatory and get the customer to agree thats clean if they dont i'll leave the rest dirty [ esp compared to the clean bit ] TFR is bib & brace, I've done a few already with WFP and they have come up well , but not perfect , TFR should [ if it works as i've heard ] complete the job and if it doesn't it's £30 lost. If it does the job i'll make it back on 1 clean.
Also gutters fascia' etc etc even that boat on another topic, i also dropped a few hints to regular customers about cleaning there window frames and stick a couple of quid on there regular cleans as a one off.
Potentials there for a £30 investment, i think thats a no-brainer myself :