I have never had a problem with pressure and release. If it comes out of as 'nagging', it is exactly what I always warn against. Never, never nag and peck at a horse. People that have ANY problems with 'pressure and release' are simply not doing it correctly.
When pressure and release is done correctly, the pressure is firm enough in the beginning for the horse to move from it. It should never be released until the correct response from a horse is received.
Spoiled horses will give a LOT of 'push back' and sometimes require a LOT of pressure to change their bad attitude. It is always better to 'over-correct' and then back off than to use too little pressure. Too little pressure often results in a horse more resolved to push -- sometimes to the point of attack. A horse that has been at the top of your 'pecking order' of two (you and the horse) sometimes gives up that top spot very reluctantly. If you use 'pressure and release' correctly, good manners can be established in a couple of sessions.
The idea that you would try to teach a horse to invade your space and 'give kisses' when the same horse would lay its ears back at you (a very direct threat) and does not have very basic manners that keep it out of your space tells me that you do not understand horse behavior and horse interaction between each other and people. You MUST be at the top of your pecking order of 2.