Hi Len
Don't use white spirit it's very unstable and if the carpets have a secondary backing it will loosen the latex
causing delamination and loosening of tufts.Often when you go into a property where the client has used white spirit you will see that there is what appeares to be a bubble under the carpet this is the reason why.
Not quite sure about Nicks method I would be worried about bursting the pile, of course you could nap of the pile by how low do you go.?
For Gloss paint you can use (with practice) Nitromors, you apply the gel,work it in with a scraper removing the excess as you go,keep your extracta at the ready to keep flushing out.
This method works very well especially on Axminsters and Wiltons but is time consuming so costs will be high and there is no guarantee of success.
Good Luck
