The hot systems wrk well with egg, but I have to honest, if that egg has dried on for a day or three or a week or two then WFP won't get close to it, once it has set you need detergent and a scraper, simple washing with an applicator isn't any good either.
Egg.
Truly horrible to get off whatever method used.
If it is no more than a day or so old WFP will shift it no problem at all and it is also easier and quicker to wash out your bristles after you have done so.
With trad oce you have dipped your applicator back into your bucket a couple of times you will have killed all the suds in your bucket and the smell of the water left in there is rank, ditto on the applicator sleeve
A dollop of baked on seagull poo will also see you come up short with WFP, that's another one where it really needs a scraper.
Stay there washing long enough and you'll get it off of course, but time is money and having your water running constantly is wasteful too!
But none of the above are reasons
not to get WFP, they are merely examples of conditions when you may need to use other tools.
WFP is afterall just one (albiet the main one) tool you use during your working day.
Ian