Well, Palmer errs on the side of caution IMO in that chapter. I toast grain all the time and have never let it sitt 2 weeks prior to using it, that is not necessary. I have toasted grain and used it that day with no prob!! But normally after toasting, I cover the cookie sheet with the grain on it with a towel and let it sit over night to cool. I never get harsh flavors from the malt by doing this. Here my normal procedure:
I use directions from " Old British Beers and How To Make Them".
Put grain on cookie sheet, place in oven heated to 110º C (230ºF)for about 20 mins to dry the grain a bit, then raise to 150º C (300º F) for 20 min. If you cut the grain, it will be a light buff or just a shade different color than untoasted malt, this is Pale Amber, another 10-20 min and it will be slightly darker and that would be Amber malt. For brown, at this point raise the temp to 175º C (350º F ) for another 20-45 mins . Cut a couple grains, the color should be full buff or the color of a paper bag on the inside, this will be brown malt. Keep in mind, you judge the color by checking it on the inside, if you go by the color of the husks, you will basically either make black or burnt malt!! Also, the times stated are ball park, I have toasted grain in the shortest times, skipping the drying step and have produced great stuff !! You need to monitor the malt as you go to get it right.