How to specify "for the duration of this activity"?

I have an activity, which has two resources assigned to it. The main effort comes from the first resource.

The second resource is support-provider, and he is lightly engaged with that activity as long as it runs. (say, at the rate of 1 hour per day).
(This is a typical scene with a consultant.)

But how to specify this in the Assignment?

The work-around seems to be very long-winded:

1. Estimate the total effort (in hours) required by Resource#1, and enter it in against the task.
2. Convert this number with the working hours/day to find how many working days are needed.
3. Calculate how many of consulting hours are needed for this activity, at the rate of 1 hour per day.

So, if the activity is going to last for 10 days, we allocate 10 hours to resource#2 (calculated at the rate of 1 hour per day).

What happens when the task requires more time to complete:

Suppose resource #1 reports a few hours of left work and asks for extension of the activity,
ProjeQtor will not automatically extend the assignment of Resource #2 to the activity.
We have to manually adjust the remaining work for him.

How to avoid that, and make it fully automatic?

No, perhaps my question was not clear.

We have already assigned the second resource at (say) 10%. But because we specify the effort hours for each user, his effort reaches 100% (no left work) when the original deadline for the task is reached.

But the first resource could not finish his work, so he wants extension.

During this extended period, resource 2 is not prompted to work, because his contribution is over (total x hours, at 10% FTE).

This is why we need to specify that the 2nd resource must go on working till the end of the task, at the same % of FTE.

I do understand that, but when the task is split among multiple resources, any delay/extension of the task would require re-planning for all those resources.

Any one of the resource can request extension of the task at any time (by entering some left work). But the software does not warn the others about this proposed extension. Of course some of the resources may not have to extend their work on this task, but some may have to stay till the very end of the task. So they will have to match the duration.

In fact, there is one more use case: Some of the resources may not be available if the task is delayed/extended; or their original allocation to this project may be expiring.

All these use cases are not handled in ProjeQtor.