What Jack said, but know - maple is easiest of all, mahogany about middle of the road, other woods can be more work intensive, but not "harder".
The key is the filling. I think probably its best to scrape" the filler into the grain, and then flush with the wood. Let it dry - then let it dry again. Sand. Repeat. Fill can actually sink into the wood! So go ahead and repeat it once more even if you think "its all filled".
After that the finish is no harder to apply.
Filling grain is not hard. Its time consuming, but easy. I mean... just dribble some on, scrape it in, scrape flush. Then set it aside and sand it. You can sand the first fills with 220grit, then 320 on the last fill. You can finish over 320g sanding with no problems, providing you sanded with the grain.
Finishing goes very very nicely on filled wood. What you'd waste in finishing time, you'll save in filling time. That is... if you spend time filling, the finish will go on, and be perfecto much more quickly.