Well, I'll tell you what I do. I won't go through the entire piece. I don't know which sections you're having trouble with. At the beginning, I use the pedal, and clear at the beginning of each set of 6 16ths. But in measure 3 when it switches to staccato I don't use any pedal. M. 9 - I pedal the arpeggio, and don't pedal for the next 6 beats. M 17-21, I use pedal very very sparingly through here. At 23 I use again, every set of 6 16ths. M 27 - I use it again very sparingly. At the beginning of the cantabile I pedal every half measure or, occasionally I'll break a little more depending on what the harmony is doing. At 59, I try not to pedal as much as possible, with the exception of the ascending octaves. And then when it gets to octaves in both hands I don't pedal at all. In the leggiero section, I also use very little pedal. Typically I'll use it to play the LH octave at the beginning of the measure where there is one (Ex - mm 75, 76, 78, 79) but not if there's just a single note and not the whole octave.
Personally, I think if you use too much pedal in this piece it gets too mushy and loses it's crispness. So you're welcome to try my ideas, or completely scrap them and come up with your own. If you have more questions about specific sections, feel free to send me a PM.
Topic: need help pedaling mendelssohn fantasy op.28