Kurotowa said:
Sure, you can try to improve a disguise by changing your clothes. But that just means you re-roll your disguise check with a better circumstance modifier. I know of no situation where you can improve a skill check's result after you make the check.
So, I guess you only get to make one Disguise check per disguise, huh?
SRD said:
DISGUISE (CHA)
Check: Your Disguise check result determines how good the disguise is, and it is opposed by others’ Spot check results. If you don’t draw any attention to yourself, others do not get to make Spot checks. If you come to the attention of people who are suspicious (such as a guard who is watching commoners walking through a city gate), it can be assumed that such observers are taking 10 on their Spot checks.
You get only one Disguise check per use of the skill, even if several people are making Spot checks against it. The Disguise check is made secretly, so that you can’t be sure how good the result is.
So, the question then becomes, "What constitutes a 'use of the skill'"?
Obviously, it must be a complete disguise.*
If you are using both Alter Self and Disguise Self to make a single disguise, then both bonuses apply.
* - Why must it be a complete disguise?
Because to assume otherwise leads to all kinds of stupidity. Let's assume that a thin human male wants to disguise himself as an elven female. In order to make his disguise, we'll assume that he must alter his ears, his eyebrows, and his bustline, as well as apply some make-up.
When do you make the disguise roll?
According to those who say that the two spells / abilities may not be used in concert, you must here make 4 separate Disguise rolls: once to disguise himself as a human with funny ears, once to disguise himself as a human with altered eyebrows, once to disguise himself as a human male with breasts, and once to disguise himself as a human male wearing some make-up.
Why such craziness? Because:
Kurotawa said:
But that just means you re-roll your disguise check with a better circumstance modifier.
So, he gets slightly better circumstance modifiers each time he adds something new to his disguise, and since the results of the previous disguise are "discarded," this requires four rolls with increasingly better modifiers.
Do you agree that this is a pretty silly way to rule?
Then, similarly, altering your physical form as
one aspect of a disguise, followed by cloaking yourself with illusion magic as
another aspect of that same disguise, are summed up with a single Disguise check with the appropriate modifiers. The two spells / abilties
must stack.