There are a couple of ways to gather more clues on physical bear size to avoid shooting "mitten" bears.
One is to always be mindful of the size of the trees and in particular stumps in the area you are hunting. It's hard if all there is are little Lodgepole pine, but if there are big old Doug or Grand Fir or even big old Ponderosa Pines those stumps and trees will give a general marker of relative size.
Another is to learn to use your scope reticle in an unloaded gun to calculate size (depth and nose to tail). That can either be marked mil/moa dot system or a simple duplex. You need to have a range finder and you are good to go.
If its an ffp dot reticle, do the math after determining the distance (look up the formula for either moa or mil). Do a little dope card with the formula and carry it with you.
For an sfp duplex, just set up a 6'x3' piece of cardboard at various distances and record the gaps or spillover out of the fine reticle at 3/6/9x and create a mini "size dope card". If you know at 200 yards on "x" power there should be "x" spillover into the coarse reticle then you have a have a rough starting point. Not perfect, but a good start.
Patience above all is the key to bear hunting.