Counting in tens is easier than to count in fives and twos. I don't know why most curriculum states that children should count in twos then fives then tens. When teaching children to skip count I always start with tens, then fives, then twos.
A quick and painless way to get children to learn to count in tens is to do it informally first. Whenever I want children to pack up, line up or whatever, instead of counting from 1 to 10 I would count by tens to 100. I do this consistently and eventually children will start to join in with the counting. When most children have memorised the tens sequence I then move onto counting by fives, then finally by twos. This becomes the basis for more formal lessons in number patterns and place value (counting in tens) (and later on, times tables).
To start off, children have lessons with base 10 shorts (units/ones) and longs (rods/tens). However, there will be some children who can count in tens but do not really understand the concept of tens and ones. To counteract this I provided many opportunities to work in tens.
We've bundles pop sticks.
We've stacked counters.
We've linked chains.
We've also connected unifix cubes, grouped counters, beaded buttons - anything that could be connected, joined, or grouped into tens. Alhamdulillah, after these hands on activities, the children have a deeper sense of counting in tens and for those who were more advanced, they have also benefited. Their understanding was deepened by asking them to combine their tens with their neighbour's and skip count beyond 100.