that's what i read, but my success rate was at 0% until i waited at LEAST 6 month (i did get one to take for a a couple weeks and he got bigger, but ended up turning yellow and falling off - there was no visible rot).  my working space and utensils were all sterilized, and the procedure was done exactly the same as my later grafts (all of which took but one, but that was because i tried a humidity tent and it rotted).

grafting is definitely better in the spring, especially if you live in a cold/not well lit climate (like me).

in fact i have my pere and achuma seedlings all ready to go, just waiting for the right weather.