Raising the temp slowly to about 85-86 and adding some salt can be used in combination with medication.
Some people swear by just heat with or without salt and frequent large waterchanges to get rid off ick - I have tried it but it was not fully effective for me.
I have successfully treated plecos in the past with a combination of Formalin and Malachite green. This combination is present in most common Ick medications.
When you medicate just follow the directions on the bottle and do it in combination with raised temperature , increased airaition, stop feeding and large waterchanges (50%)
When I treat for Ick I do a 50% change before each treatment and do treatments on days:1, 3,6 and 10 at which point they should be cured. At day 12 do a large waterchange and filter with activated carbon.
Make sure it is Ick and not Oodium (Velvet) which also presents itself as small white spots but smaller then ick . If it is Oodium it is much nastier and you need to put the lights out and cover the tank in addition to the treatment . Also keep treating for 30 days with additional treatments on day 15 , 20 and 28 - finishing with waterchange and carbon on day 30.
Best of luck