Thanks for confirming that there isn't any set tightening order. I just did a crisscross pattern with gradual tightening all around. I do want to note that the torque specs on that website are not accurate. Haynes 3MZ-FE manual shows 71 in-lbs for the both front and rear valve covers. Moreover, there was another gentleman who commented on a youtube video that he noted that the Toyota's 3MZ-FE shop manual showed 71 in-lbs also (however, I can only personally attest to the Haynes Manual which I own). In that DIY youtube video, the mechanic relied on the website you suggested and overtorqued the valve cover bolts to 9 ft-lbs (108 in-lbs), causing one of this bolts to break! So, I would highly suggest following more reputable sources like Toyota/Lexus service manuals and Chilton/Haynes Manuals.