Not heared about a change to the formula but when i apply Hammerite i always stipple it on as apposed to brushing.
I once stipple painted the whole body of a cf van in the blue colour and it looked brilliant.

Phoned Hammerite a while back , was told that it is now white spirit based. It wont take acrylic lacquer like it once did and the number one anti rust primer ive found reacts with many top coats. I have used it for many years but no more, there are better products out there regards Chris.