Poorboys Trim Restorer or Duragloss Rubber and Mat Dressing seem to be the best one's that I've worked with of late... The Duragloss has a rain repel agent in it as well so seems to hold up very well so far...... The Trim Restorer or even the Clearkote Vinyl / Rubber Treatment (the two are VERY similar), are more oil based dressings but this in itself means they will work on large areas of trim better than a waterbased dressing at this time of year, given the unfavourable weather.

Cheers.