Clit becomes as sensitive after orgasm as the head of your penis is. As far as I know from the reactions of males - they do not enjoy their penis head sucked, flicked or touched immediately after orgasm. I know that I don’t want anything near my clit after I cum.

It is uncomfortable to say at least, if one persist it does become painful.
Will it do any damage? As long as the touch / play is not violent and does not constrict the blood flow - NO to the best of my knowledge. You may piss her off, make her beg/cry and not want to have anything to do with you - but you will not damage her with your tongue, nor will you do damage with your hand (likely). Tools and toys are to be used with caution.

Pumping … Google it! there is many pumping sites and resources. The pressure, the length of session … it all depends on the person mostly. Some will find the sensation very erotic and arousing, others unbearably painful. The cheapest way to go with testing the pumping is to get “snake bites” or cheaper even the little insulation caps that you slip on the jump-cables for car. They work great for the nipples and clit as well - and are much cheaper for experiment than the “official” pump (that might not get work out for what is worth!) Another home made “pump” is made out of plastic syringe. Cut off the part that you append needle to and than slide the inside (apologies for this - brain took vacation so it seems, can not dig out the words) “plunger thingie” from that newly cut side (because the edges are going to be rough and can cut/damage sensitive skin).

Have fun - and pay attention to her and body parts in question - in general colour change to dark purple is good only for short period - than release. And if she is screaming in genuine pain . well use your discretion