There's a couple different schools of thought to flaps on takeoff when flying soft/short field. If the 206 I was going to fly had 5 pax and bags in the back... the tail sits maybe 7 inches off the ground... so no need to pull all the way back on that control wheel to keep the nose light and protected on the rough runway. Normally I would have flap 10 set before the roll.... flaps 20 would come in handy when you had a impala or goat or whatever jump out on the runway last second... no time left to stop but enough speed to get into ground effect...drop the 20 and up you. Never would I start the takeoff roll with 20... that's just too much unnecessary drag on the roll... better to drop to 20 last second if you are about to balloon up to safety. Some pilot will opt to start the takeoff roll with 0 flap to get up to speed asap then drop to 10 or 20 for an early up well...
In the caravan, flaps 20 is standard for takeoff... dropping to 30 (full flap) last second helps to get up early too... just don't try and escape ground effect too soon! Starting a roll with full flaps 30 is approved if you have the APE stall kit... comes in handy if the nose wheel's going to take a beating on the runway since full flap will get that nose up into a wheelie right away with the control wheel full back. Then just wheelie it out until the plane is ready to get airborne. Just need to make sure your nose wheel is barely off the ground... otherwise the flaps are introducing way too much drag and killing your effort to make a short takeoff roll.
Of course a flap motor failure / asymmetric flaps could always happen so be ready for the consequences. Playing with flaps on takeoff in the bush certainly has its merits. However, using flaps 30 for takeoff is not a good idea in a short caravan... in an engine failure you'll lose the effectiveness of your elevator, and depending on CofG, unable to pitch down for a stall recovery. Also it's not approved.
I am curious though, how do you float guys typically use your flaps for takeoff? Looking for some insight from the float world!