I've used this toner 1+3 and 1+9 on Kentmere Fineprint Gloss (not warmtone), and also on the warmtone FG matt surface at 1+3.
It tones very fast, and there is an eggplant cast at all dilutions I've tried, but only subtly on the gloss paper at 1+9 - I had to compare to an untoned print to spot the difference. The most I have toned for is 4 minutes, and there is a noticeable difference after 1 minute with the stronger dilutions.
No problems enhancing the Dmax. More noticable on the gloss paper, which produces wonderful deep blacks anyway, the toner separates things just that bit further.
You might find you need to print at a higher grade than Ilford paper to get a good Dmax, but I've only used Ilford RC so I could be comparing apples to oranges.