Separating the tire from the rim is always the toughest part. Standing on the tire, blocks of wood, trying to use screwdrivers etc. has never proved successful for me.
I suggest getting (buying/borrowing) a simple bead breaker tool (go to HarborFreight.com and search for Bead Breaker). Turns the job from frustrating to simple.
Also, for safety, don't fully inflate until the wheel is back on the gear and the big nut is screwed on (unless you have a tire cage). The nut is put on snug, but not tight - the alignment of the holes for the cotter pin will be your guide.
It is a good time to repack your wheel bearings and check the brake pads, while everything is apart.
Dennis Glaeser CFII
Rochester Hills, MI
RV-7A - Eggenfellner H6, GRT Sport EX, EIS4000, 300XL, SL30, TT Gemini, PMA6000, AK950L, GT320,
uAvionix Echo ADSB in/out with GRT Safe Fly GPS