painting weights, unable to reduce the amount, 3dsmax 2013 student version

[iz7749]

i am trying to learn rigging for character models however when i try and paint weights after adding a skin modifer and adding the bones i am unable to reduce the painted weights, ive tryed editting the settings but that didnt help, i am still able to add weight to polygons and change the ammount at which they add but i cant remove existing painted weights or remove those i add. which makes it nearly impossible to learn because i obviously need to "rub it out" for want of a better phrase. after watching a tutorial the person said to hold alt to remove the painted weight but that didnt work and ive tryed every combination of shortcuts i could think of. eveerything else works fine, its only this. ive re-downloaded, repaired, should be up to date. it just doesnt want to work. the same thing happened in 2012 which is reallt confusing as i am now using a different version aswell as a different computer. any help is greatly appreciated, thanks. 

[OzzyH]

The best way to apply weights is to use Vertex and then changing the Absolute Value parameter to your desired result. Try not to reduce the weight values for a given bone instead select a neighbouring bone and assign some weight for it. For example if you got a cylinder and with two bones (say upper bone and bottom bone) and in the middle of that cylinder on some vertex you have assigned weight for upper bone to 1 but you want to reduce it to 0.5 for upper bone then you need to increase the Absolute value for the bottom bone of that same vertex to 0.5 this will give bottom and upper bone 0.5 weight influence on that vertex. Hope that helped