Looks good with no residue depends entirely on number of rinses and dust level. Beware Apple has moisture sensors to invalidate warranty may be triggered. by changing colour on test coupons scattered near board and battery on iMac, iPad and maybe iPhone.
Also beware Apple and others use "no clean flux" which is corrosive with moisture and air so forced air drying is critical for long periods to get under chips with exposed solder/copper interface.
A nylon tooth brush is Ok for me with any finger on ground plane (to bleed any possible static build up) and speeds up the process. I also use a central vac, but I don't recommend if you are not sure about flammability, but I use a bottle of ISOPROPYL alcohal instead which has high water content and needs vacuum assist with forced room air drying. This has recovered several keyboards and laptops dead from spilt fluids including beer. Just make sure rust hasn't started from moisture ingress (rain) from the no-clean flux (oximoron) and get it cleaned quickly.
This anti-oxidant is a excellent for RF contacts , USB and power contacts.
some LCD's use antiglare surface prep which can be dissolved but iPads do not with gorilla glass. – Tony Stewart