if you have to wear thripundraka bhasmam (pasted holy ashes in three parallel and horizontal strands) in the evening, you have to take a bath.. or something equivalent to bath.(there are many substituted rituals equivaltent to bath.. but a strightforward bath in a riverside, pond on under a shower is the best). and for performing sayam sandhya full bhasmadharanam( wearing of holy ashes ritualistically) is a must for smarthas..
(Of course I have read some texts where it is prescribed that ashes should not be soaked in water if they are worn in the evening..
But as a shistacharam, I have seen most bramins in Palakkad wearing holy ashes soaked in water too.. in the evening... provided they take bath..
Of course, there cannot be any hard and fast prescription for this in Vedas or major Smritis.. It comes rather by tradition)
Dont know what vaishnavism prescribes about sreechurnam and gopi.. that is their secret.. I am an out and out shaivite..
We have now forgotten performing maadhyahnikam..
If we are doing madhyahnikam, sastras prescribe a bath just before midday and then also vibhuthi has to be worn in detail
Sure, vibhuti pattai(or smear of holy ashes made into a semisolid paste) is to be worn all over the body, at least on selected sixteen on eighteen places on the body.. and not only on the forehead..
the vibhoothi lines should never be crossed with any other pottus (other tilaks or marks) or ornamentation like sandal paste, kumkumam etc..
The rules are elaborate and strict.. , this Pattai with viboothi is a very serious affair..
Acts of omission or disrespect of the holy ashes will enrage the killer of killer Lord Shiva and you can guess what can happen..
But the rules are even more strict for pure Shaivas.. like Sivacharyas, Gurukkal etc, who perform poojas in our Shiva temples..
Among Lingayattas, men and ladies too wear thripundrakam and also wear Shivalinga in their upper body..
Thripundrakam is not usually prescribed for our smartha ladies .. although some old paattis(grandmas) wear it that way as per local customs..
Especially elderly widows who have been initiated to Panchaksharam sometimes wear thripundra..
In fact they can wear only dry holy ash in a single line.
That practice of wearing elaborate marks with ashes mixed in water may be right for the old ladies according to the custom , but our smrithis do not prescribe it.. It is again a tradition.