How to express a post that is longer?

If you are not comfortable in reading and responding long posts, do not do so. it is no harm. with time with more post you will feel easy

i'm not sure if there's really a technique on it but it depends on how you are acquainted with the subject matter on hand. putting some spice and personal experience will do good in stretching it to it's maximum but if it doesn't suits your preference then it would be very hard to write something. this is the reason why i respond only to those that i know i an contribute or i know about the topic. you just have to get the hang of it coz when i was still new here, i have the same problem as you do since i always talk and reply straight forward until i discover something while reading in some discussions here and in my experiment as well.