Whatever shears you have and whatever plants you trim, the job is much easier if you take care of your shears.

The sap which builds up on the blades makes opening and closing them more difficult, so wipe them clean with an oily rag after use (and part-way through trimming, if there's a lot to do). For ease of use and cleaning, consider buying shears with stainless steel or Teflon-coated blades. Stainless steel doesn't go rusty and Teflon-coated blades are easier to clean than ordinary ones.

Check the blade tension is correct and oil the pivot point regularly.

Some shears are self-sharpening. If not, check whether one or both blades have a cutting edge, and sharpen that edge at the same angle with a sharpening stone (a whetstone - from Felco, Multi-Sharp, or hardware/DIY shop).