New bath waste unit, removing old silicon?

[garmcqui]

It looks like I need to fit a new bath waste unit. The old pop up mechanism isn't working.

I understand it's best to use some silicon to seal the waste, in addition to the rubber washers etc provided. However, is it necessary to remove all the old silicon that has been used? If yes, using what?

Also, I have some Fernox LS-X, is this suitable or is ordinary silicon better?

Thanks,

 

[just pumps]

There are silicone removers however you still need to scrape off the remains to give a clean face. Most guys will use silcone but a few will use plumbers mait.